WPZ Williams Partners, L.P. Common Units Representing Limited Partner Interests (delisted)

IMPORTANT NOTE ABOUT THIS JOINT CONSENT STATEMENT/PROXY STATEMENT/PROSPECTUS

This joint consent statement/proxy statement/prospectus incorporates by reference important business and financial information about Williams and Williams Partners and their respective subsidiaries from documents filed with the Securities and Exchange Commission (“SEC”) that have not been included in or delivered with this joint consent statement/proxy statement/prospectus. This information is available without charge at the SEC’s website at www.sec.gov, as well as from other sources. See “Where You Can Find More Information.”

Holders of outstanding WPZ Units and holders of outstanding shares of Williams Common Stock may also request copies of these publicly filed documents from Williams or Williams Partners without charge, upon written request to One Williams Center, Tulsa, Oklahoma 74172-0172, Attention: Investor Relations or by calling the Williams Partners’ or Williams’ Investor Relations Departments at 800-600-3782.

In order to receive timely delivery of requested documents in advance of the Williams Special Meeting, your request should be received no later than August 2, 2018. If you request any documents, Williams or Williams Partners, as applicable, will mail them to you by first class mail, or another equally prompt means, after receipt of your request.

Except as otherwise specifically noted, or the context otherwise requires, as used in this joint consent statement/proxy statement/prospectus:

In “Questions and Answers” and in the “Summary” below, selected information from this joint consent statement/proxy statement/prospectus is highlighted, but not all of the information that may be important to you is included. To better understand the Merger Agreement and the Merger, and for a more complete description of its legal terms, you should carefully read this entire joint consent statement/proxy statement/prospectus, including the section entitled “Risk Factors” on page 19, as well as the documents that are incorporated by reference into this joint consent statement/proxy statement/prospectus. See “Where You Can Find More Information.”

You should rely only on the information contained or incorporated by reference in this joint consent statement/proxy statement/prospectus. None of Williams, Williams Partners, or any of their affiliates has authorized anyone to provide you with information different from that contained or incorporated by reference in this joint consent statement/proxy statement/prospectus. Therefore, if anyone gives you information of this sort, you should not rely on it. The information contained in this joint consent statement/proxy statement/prospectus and the documents incorporated herein by reference is accurate only as of its respective dates, regardless of the time of delivery of this joint consent statement/proxy statement/prospectus. Williams’ and Williams Partners’ business, financial condition, results of operations and prospects may have changed since those dates.

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QUESTIONS AND ANSWERS

The following section provides brief answers to certain questions that you may have regarding the Merger Agreement, the proposed Merger, the Charter Amendment, and the Stock Issuance. Please note that this section does not address all issues that may be important to you as a Williams Stockholder and/or a WPZ Unitholder. Accordingly, you should carefully read this entire joint consent statement/proxy statement/prospectus, including each of the annexes, and the documents that have been incorporated by reference into this joint consent statement/proxy statement/prospectus.

General Questions and Answers

Q. Why am I receiving these materials?

A. Williams and the WPZ General Partner have agreed that Merger Sub, a wholly owned subsidiary of Williams, will merge with and into Williams Partners, with Williams Partners surviving as a wholly owned subsidiary of Williams.

Each of Williams and Williams Partners is sending these materials to the Williams Stockholders and the WPZ Unitholders, as applicable, to help them decide how to vote their shares of Williams Common Stock, or deliver their consent with respect to their WPZ Units, regarding the matters described herein.

This document constitutes both a proxy statement and prospectus of Williams, and a consent statement of Williams Partners. This document is a proxy statement because the Williams Board is soliciting proxies from the Williams Stockholders in connection with the approval of the proposed Charter Amendment and Stock Issuance. This document is a consent statement because WPZ Unitholders are being afforded the opportunity to sign a written consent to the Merger using this document. This document is a prospectus because Williams, in connection with the Merger, is offering Williams Common Stock in exchange for outstanding WPZ Public Units.

Q. What will happen to Williams Partners as a result of the Merger?

A. If the Merger is successfully completed, Merger Sub will be merged with and into Williams Partners, with Williams Partners surviving as a wholly owned subsidiary of Williams. Following the closing of the Merger, it is expected that Williams Partners will merge with and into Williams, with Williams surviving, and Williams Partners will cease to exist.

Q. When will the Merger be completed?

A. Williams and Williams Partners are working to complete the Merger as soon as possible, but the Merger cannot be completed before the day following the record date for the regular quarterly cash distribution on the WPZ Common Units that is paid or payable during the calendar quarter ending September 30, 2018. A number of conditions must be satisfied before Williams and Williams Partners can complete the Merger. Although Williams and Williams Partners cannot be sure when all of the conditions to the Merger will be satisfied, Williams and Williams Partners expect to complete the Merger as soon as practicable following the Williams Special Meeting (assuming the Stock Issuance and the Charter Amendment are both approved at the Williams Special Meeting). See the section titled “The Merger Agreement — Conditions to the Merger.” Assuming timely satisfaction of other closing conditions, including approval of the Stock Issuance and the Charter Amendment at the Williams Special Meeting, the Merger is targeted to close on or about August 10, 2018.

Q. What percentage of outstanding Williams Common Stock will WPZ Public Unitholders own after the successful consummation of the Merger?

A. If the Merger is successfully completed, based on the number of shares of Williams Common Stock and WPZ Units outstanding as of the date of this joint consent statement/proxy statement/prospectus, the shares of Williams Common Stock that the WPZ Public Unitholders receive in the Merger will collectively represent approximately 31.6% of the outstanding shares of Williams Common Stock following completion of the Merger.

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Q. Who do I call if I have further questions about the Merger Agreement, the Merger, the Charter Amendment, or the Stock Issuance?

A. If WPZ Unitholders or Williams Stockholders have further questions or if they would like additional copies, without charge, of this document, they may call Williams Partners’ or Williams’ Investor Relations Departments at 800-600-3782, or may contact OKAPI Partners LLC (“Okapi”), which is acting as Williams’ proxy solicitation agent in connection with the Williams Special Meeting, by phone at (888) 785-6617 or email at williamsinfo@okapipartners.com.

Q. What happens if the Merger is not consummated?

A. If for any reason the Merger is not consummated, WPZ Common Units will continue to be listed and traded on the NYSE.

If the Charter Amendment Proposal is approved, the Charter Amendment will be effected, regardless of whether the Merger is consummated.

Questions and Answers Specific to Williams Stockholders

Q. When and where will the Williams Special Meeting be held?

A. The Williams Special Meeting will be held on August 9, 2018 at 10:00 a.m., local time, at One Williams Center, Tulsa, Oklahoma 74172-0172.

Q. Who is entitled to vote at the Williams Special Meeting?

A. If you are a record holder of Williams Common Stock as of the close of business on the Williams Vote Record Date, you may vote at the Williams Special Meeting. See the section titled “The Williams Special Meeting of Stockholders” beginning on page 27 of this document.

Q. What are Williams’ Stockholders being asked to vote on at the Williams Special Meeting?

A. Williams Stockholders are being asked to consider and vote on the following proposals:

Q. What vote is required to approve each of the Proposals?

A. The approval of the Charter Amendment Proposal requires the affirmative vote of holders of a majority of the outstanding shares of Williams Common Stock entitled to vote thereon. The approval of the Stock Issuance Proposal requires the affirmative vote of a majority of the votes cast on the proposal at the Williams Special Meeting, provided a quorum is present. The approval of the Adjournment Proposal requires the affirmative vote of a majority of the votes cast on the proposal at the Williams Special Meeting, regardless of whether a quorum is present.

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Q. What constitutes a quorum for the Williams Special Meeting?

A. The presence, in person or by proxy, of Williams Stockholders representing a majority of the shares of Williams Common Stock outstanding on the Williams Vote Record Date will constitute a quorum for the Williams Special Meeting.

Q. What if I do not vote my Williams Common Stock or if I abstain from voting?

A. The Stock Issuance Proposal and the Adjournment Proposal each require the affirmative vote of a majority of the votes cast on such proposal at the Williams Special Meeting (provided in the case of the Stock Issuance Proposal that a quorum is present). Abstentions will be counted as votes cast for purposes of the Stock Issuance Proposal, but will not be treated as votes cast for purposes of the Adjournment Proposal. As a result, if you abstain from voting on the Stock Issuance Proposal, your shares of Williams Common Stock will be counted as present for purposes of establishing a quorum, but the abstention will have the same effect as a vote against that proposal. If you abstain from voting on the Adjournment Proposal, your shares of Williams Common Stock will be disregarded for purposes of determining the votes cast for the Adjournment Proposal, and the abstention will therefore have no effect on the adoption of that proposal. If you fail to vote on the Stock Issuance Proposal or the Adjournment Proposal, such failure to vote will not affect the adoption of such proposal, except with respect to the Stock Issuance Proposal to the extent that your failure to vote prevents the establishment of a quorum at the Williams Special Meeting.

The approval of the Charter Amendment Proposal requires the affirmative vote of holders of a majority of the outstanding shares of Williams Common Stock entitled to vote thereon. As a result, if you do not vote your shares of Williams Common Stock in favor of the Charter Amendment Proposal or abstain from voting on the Charter Amendment Proposal, it will have the same effect as a vote against the Charter Amendment Proposal.

The obligations of the parties to complete the Merger are conditioned upon approval of both the Charter Amendment Proposal and the Stock Issuance Proposal (collectively, the “Williams Stockholder Approval”). Accordingly, a vote against or an abstention with respect to either of such proposals will have the same effect as a vote against the Merger (although no vote for or against the Merger is taking place).

Q. What proposals at the Williams Special Meeting must be passed in order for the Merger to be completed?

A. The Merger will not be completed unless the Charter Amendment Proposal and the Stock Issuance Proposal are each approved. If the Charter Amendment Proposal is approved, the Charter Amendment will be effected, regardless of whether the Stock Issuance Proposal is approved and the Merger is consummated.

Q. How do I submit my proxy for the Williams Special Meeting?

A. If you are a stockholder of record, you may submit a proxy via the Internet, by phone, or by mail. If you hold your Williams Common Stock in “street name” with a broker, bank, or other nominee, you should follow the instructions provided by your broker, bank, or other nominee. See the section titled “The Williams Special Meeting of Stockholders” beginning on page 27 of this document.

Q. How many votes do I have?

A. Williams Stockholders have one vote per share of Williams Common Stock on each proposal to be voted upon.

Q. If my shares of Williams Common Stock are held in street name by my bank, broker, or other nominee, will my bank, broker, or other nominee automatically vote my shares for me?

A. No. If your shares of Williams Common Stock are held in street name, you must instruct the broker, bank, or other nominee on how to vote your shares. See the section titled “The Williams Special Meeting of Stockholders” beginning on page 27 of this document.

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Q. What happens if I sell my Williams Common Stock after the Williams Vote Record Date but before the Williams Special Meeting?

A. If you transfer shares of your Williams Common Stock after the Williams Vote Record Date but before the date of the Williams Special Meeting, you will retain your right to vote at the Williams Special Meeting.

Q. May I change my proxy instructions after I have delivered my proxy card?

A. If you are a stockholder of record, you can change your proxy instructions within the regular voting deadlines by submitting a new proxy by telephone or via the Internet, executing and returning a later dated proxy card, or attending the Williams Special Meeting and voting in person. If you are a stockholder of record, you can revoke your proxy by delivering a written notice of your revocation to Williams’ Corporate Secretary at One Williams Center, MD 47, Tulsa, Oklahoma 74172. If you hold your Williams Common Stock in street name, you should follow the instructions provided by your banker, broker, or other nominee. See the section titled “The Williams Special Meeting of Stockholders” beginning on page 27 of this document.

Q. Will I receive anything as a result of the Merger?

A. As a Williams Stockholder, you will not receive any consideration in connection with the Merger. Only WPZ Public Unitholders will receive consideration in connection with the Merger. Williams Stockholders will not be entitled to appraisal rights in connection with the Merger.

Questions and Answers Specific to WPZ Unitholders

Q . Who is entitled to give written consent with respect to the Merger?

A. If you are a record holder of WPZ Units as of the close of business on the WPZ Record Date, you may give written consent with respect to the Merger by filling out the enclosed written consent, dating and signing it, and then promptly delivering it to Williams Partners by one of the means described in the section entitled “Written Consents of Holders of WPZ Units — Submission of Consents.” Williams Partners does not intend to hold a meeting of WPZ Unitholders to consider the Merger Agreement and the Merger.

Q. Can holders of WPZ Units change or revoke their written consents?

A. Yes. If you are a record holder of WPZ Units on the WPZ Record Date, you may revoke your consent or, if you have previously revoked your consent, submit a new written consent at any time before the consents of a sufficient number of WPZ Units to approve the Merger Agreement have been delivered to the secretary of Williams Partners. If you wish to change or revoke your consent before that time, you may do so by sending in a new written consent with a later date by one of the means described in the section entitled “Written Consents of Holders of WPZ Units — Submission of Consents,” or delivering a notice of revocation to the secretary of Williams Partners.

Q. What WPZ Unitholder approval is required to adopt the Merger Agreement?

A. The approval and adoption of the Merger Agreement and the Merger by Williams Partners requires the affirmative vote or consent of holders of a majority of the outstanding WPZ Units. Pursuant to the terms of the Support Agreement, Williams Gas Pipeline, which as of May 15, 2018 beneficially owned 702,218,502 WPZ Common Units and 18,442,649 WPZ Class B Units representing approximately 73.8% of the outstanding WPZ Units, has irrevocably agreed to deliver the WGP Written Consent within two business days after the effectiveness of the registration statement of which this joint consent statement/proxy statement/prospectus forms a part. The delivery of the WGP Written Consent by Williams Gas Pipeline with respect to the WPZ Units it owns will be sufficient to adopt the Merger Agreement and thereby approve the Merger on behalf of Williams Partners.

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Q. Should holders of WPZ Units deliver their WPZ Units now?

A. No. After the Merger is completed, holders of WPZ Units who hold their WPZ Units in certificated or book entry form will receive written instructions for exchanging their WPZ Units. If you own WPZ Units in street name, the shares of Williams Common Stock you will receive in connection with the Merger should be credited to your account in accordance with the policies and procedures of your bank, broker, or other nominee within a few days following the closing date of the Merger.

Q. What will WPZ Public Unitholders be entitled to receive in the Merger?

A. Each WPZ Public Unitholder will be entitled to receive Williams Common Stock in exchange for such holder’s WPZ Public Units at the Exchange Ratio. If the Exchange Ratio would result in a WPZ Public Unitholder being entitled to receive a fractional share of Williams Common Stock, such holder will receive cash (payable in U.S. dollars, without interest) in lieu of such fractional share in an amount equal to the product obtained by multiplying (1) such fraction by (2) the average of the closing price of Williams Common Stock as reported on the NYSE Composite Transactions Tape (as reported by Bloomberg Financial Markets or such other source as the parties shall agree in writing) over the five-trading-day period ending on the third trading day immediately preceding the effective time of the Merger. For additional information regarding exchange procedures, please read “The Merger Agreement — Exchange of Units; Fractional Units.”

Q. Where will WPZ Units trade after the Merger?

A. WPZ Units will no longer be publicly-traded following the Merger and will be delisted from the NYSE.

Q. What happens to future distributions with respect to WPZ Public Units?

A. If the Merger is successfully consummated, all outstanding WPZ Public Units will be converted into the right to receive Williams Common Stock at the Exchange Ratio and will no longer receive quarterly distributions from Williams Partners. For a description of the differences between the rights of holders of Williams Common Stock and holders of WPZ Units, please read “Comparison of Rights of Williams Stockholders and WPZ Unitholders.”

Q . What are the expected U.S. federal income tax consequences to a WPZ Public Unitholder as a result of the Merger?

A. The receipt of Williams Common Stock and any cash in lieu of fractional shares of Williams Common Stock in exchange for WPZ Public Units pursuant to the Merger should be a taxable transaction to U.S. holders (as defined in the section titled “Material U.S. Federal Income Tax Consequences”) for U.S. federal income tax purposes. In such case, a U.S. holder will generally recognize capital gain or loss on the receipt of Williams Common Stock and any cash received in lieu of fractional shares of Williams Common Stock in exchange for WPZ Public Units. However, a portion of this gain or loss, which portion could be substantial, will be separately computed and taxed as ordinary income or loss to the extent attributable to assets giving rise to depreciation recapture or other “unrealized receivables” or to “inventory items” owned by Williams Partners and its subsidiaries. Passive losses that were not deductible by a U.S. holder in prior taxable periods because they exceeded a U.S. holder’s share of Williams Partners’ income may become available to offset a portion of the gain recognized by such U.S. holder. See the section titled “Material U.S. Federal Income Tax Consequences” for a more complete discussion of certain U.S. federal income tax consequences of the Merger.

Q. What are the expected U.S. federal income tax consequences for a WPZ Public Unitholder of the ownership of shares of Williams Common Stock after the Merger is completed?

A. Williams is classified as a corporation for U.S. federal income tax purposes, and thus, Williams (and not its stockholders) is subject to U.S. federal income tax on its taxable income. A distribution of cash by Williams to

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a stockholder who is a U.S. holder (as defined in the section titled “Material U.S. Federal Income Tax Consequences”) will generally be included in such U.S. holder’s income as ordinary dividend income to the extent of Williams’ current or accumulated “earnings and profits” as determined under U.S. federal income tax principles. Any portion of the cash distributed to Williams Stockholders by Williams after the Merger that exceeds Williams’ current and accumulated earnings and profits will be treated as a non-taxable return of capital reducing a U.S. holder’s adjusted tax basis in such U.S. holder’s shares of Williams Common Stock and, to the extent the distribution exceeds such stockholder’s adjusted tax basis, as capital gain from the sale or exchange of such shares of Williams Common Stock. See the section titled “Material U.S. Federal Income Tax Consequences” for a more complete discussion of certain U.S. federal income tax consequences of owning and disposing of shares of Williams Common Stock.

Q. Are holders of WPZ Units entitled to appraisal rights in connection with the Merger?

A. No. Holders of WPZ Units do not have appraisal rights under applicable law or contractual appraisal rights under the Williams Partners partnership agreement or the Merger Agreement.

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RISK FACTORS

You should carefully consider the following risk factors, together with all of the other information in this joint consent statement/proxy statement/prospectus, the documents incorporated herein by reference and the documents to which you are referred herein. In particular, please read Part I, Item 1A, “Risk Factors,” in the Williams Annual Report on Form 10-K for the year ended December 31, 2017 (the “WMB 2017 10-K”), and the Williams Partners Annual Report on Form 10-K for the year ended December 31, 2017 (the “WPZ 2017 10-K”) and Part II, Item 1A, “Risk Factors,” in the subsequent Quarterly Reports on Form 10-Q filed by each of Williams and Williams Partners, each of which is incorporated by reference herein. Each of these factors could adversely affect the consummation of the Merger, Williams’ and Williams Partners’ respective businesses, operating results and financial condition, and the value of an investment in Williams Common Stock. This joint consent statement/proxy statement/prospectus also contains forward-looking statements that involve risks and uncertainties. Please read “Information Regarding Forward-Looking Statements.”

Risks Related to the Merger

The number of shares of Williams Common Stock that holders of WPZ Public Units will be entitled to receive in the Merger is based upon a fixed Exchange Ratio. As a result, the market value of the shares of Williams Common Stock that holders of WPZ Public Units receive for their WPZ Public Units in the Merger could decrease prior to the consummation of the Merger.

The Exchange Ratio to be paid in the Merger is fixed (subject to adjustment if the Merger closes on or after September 7, 2018), meaning that it does not change and is not dependent upon the relative values of WPZ Public Units and Williams Common Stock. Therefore, there is no “price protection” mechanism contained in the Merger Agreement that would adjust the number of shares of Williams Common Stock that holders of WPZ Public Units will receive based on any decreases in the trading price of Williams Common Stock. If the price of Williams Common Stock decreases because of changes in Williams’ business, operations, or prospects, market reactions to the Merger, general market and economic conditions, or any other factors, such as an equity or debt offering, the market value of the shares of Williams Common Stock received by holders of WPZ Public Units will also decrease. If Williams engages in any such transactions and the market price of Williams Common Stock declines in value as a result, holders of WPZ Public Units will receive less value for their WPZ Public Units than the value calculated pursuant to the Exchange Ratio on the date the Merger was announced. For historical and current market prices of WPZ Common Units and Williams Common Stock, please read the “Market Price and Cash Distribution Information” section of this joint consent statement/proxy statement/prospectus.

The Merger is subject to closing conditions that, if not satisfied or waived, will result in the Merger not being consummated, which may cause the market price of the WPZ Units and/or Williams Common Stock to decline.

The obligation of the parties to the Merger Agreement to complete the Merger is subject to the satisfaction or waiver of certain conditions, including:

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The parties’ obligations are also separately subject to the satisfaction or waiver of the following conditions:

If these conditions are not satisfied or waived, the Merger will not occur, which may cause the market price of the WPZ Units and/or Williams Common Stock to decline.

Financial projections regarding Williams Partners and Williams may not prove accurate.

In performing their financial analyses and rendering their respective opinions, the financial advisors to the WPZ Conflicts Committee and the Williams Board reviewed and relied on, among other things, internal financial analyses and forecasts for Williams Partners and Williams, which were prepared by employees of Williams who normally render services to Williams Partners. These financial projections include assumptions regarding future operating cash flows, expenditures, and income of Williams Partners and Williams. These financial projections were not prepared with a view to public disclosure, are subject to significant economic, competitive, industry, and other uncertainties and may not be achieved in full, at all, or within projected timeframes. The failure of Williams Partners’ or Williams’ businesses to achieve projected results, including projected cash flows, could have a material adverse effect on the price of Williams Common Stock, Williams’ financial position, and Williams’ ability to maintain or increase its dividends following the Merger.

The unaudited pro forma financial statements included in this joint consent statement/proxy statement/prospectus are presented for illustrative purposes only and may not be an indication of the combined entity’s financial condition or results of operations following the Merger.

The unaudited pro forma financial statements contained in this joint consent statement/proxy statement/prospectus are presented for illustrative purposes only, are based on various adjustments, assumptions and preliminary estimates and may not be an indication of the financial condition or results of operations of the combined entity following the Merger for several reasons. The actual financial condition and results of operations of the combined entity following the Merger may not be consistent with, or evident from, these pro forma financial statements. In addition, the assumptions used in preparing the pro forma financial information may not prove to be accurate, and other factors may affect the financial condition or results of operations of the combined entity following the Merger. Any potential decline in the financial condition or results of operations of the combined entity may cause significant variations in the price of Williams Common Stock after completion of the Merger. See “The Merger – Unaudited Financial Projections of Williams and Williams Partners.”

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The Williams Partners partnership agreement limits the duties of the WPZ General Partner to WPZ Unitholders and restricts the remedies available to unitholders for actions taken by the WPZ General Partner that might otherwise constitute breaches of its duties.

In light of potential conflicts of interest between Williams and the WPZ General Partner, on the one hand, and Williams Partners and the WPZ Public Unitholders, on the other hand, the WPZ Board submitted the Merger and related matters to the WPZ Conflicts Committee for, among other things, review, evaluation, negotiation and possible approval of a majority of its members, which is referred to as “Special Approval” in the Williams Partners partnership agreement and this joint consent statement/proxy statement/prospectus. Under the Williams Partners partnership agreement:

The WPZ Conflicts Committee reviewed, negotiated and evaluated the Merger Agreement, the Support Agreement, the Merger and related matters on behalf of the WPZ Public Unitholders and Williams Partners. Among other things, the WPZ Conflicts Committee unanimously determined in good faith that the Merger Agreement and the transactions contemplated thereby, including the Merger, are in the best interests of Williams Partners and the WPZ Public Unitholders, approved the Merger Agreement and the transactions contemplated thereby, including the Merger, and recommended the approval of the Merger Agreement and the transactions contemplated thereby, including the Merger, to the WPZ Board. The duties of the WPZ General Partner, the WPZ Board, and the WPZ Conflicts Committee to WPZ Unitholders in connection with the Merger are substantially limited by the Williams Partners partnership agreement.

Certain directors and executive officers of the WPZ General Partner may have interests that differ in certain respects from the WPZ Public Unitholders.

In considering the approval of the Merger Agreement and the Merger by the WPZ Conflicts Committee and the WPZ Board, WPZ Public Unitholders should consider that some of the directors and executive officers of the WPZ General Partner who are not members of the WPZ Conflicts Committee may have interests that differ from, or are in addition to, their interests as WPZ Public Unitholders. See the section titled “The Merger – Interests of Certain Persons in the Merger” beginning on page 72 of this document.

Certain directors and executive officers of Williams may have interests that differ in certain respects from the Williams Stockholders.

In considering the Williams Boards Recommendation, the Williams Stockholders should consider that some of the directors and executive officers of Williams may have interests that differ from, or are in addition to, their interests as Williams Stockholders. See the section titled “The Merger – Interests of Certain Persons in the Merger” beginning on page 72 of this document.

The Merger Agreement contains provisions that limit Williams’ ability to pursue alternatives to the Merger, could discourage a potential competing acquirer of Williams from making a favorable alternative acquisition proposal and, in specified circumstances under the Merger Agreement, require Williams to pay a termination fee of $410 million to Williams Partners.

Under the Merger Agreement, there are restrictions on the ability of Williams to enter into alternative transactions. Unless and until the Merger Agreement is terminated or the Merger closes, subject to specified

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exceptions, Williams is restricted from initiating, soliciting, knowingly encouraging or knowingly facilitating any inquiry, proposal or offer for a competing acquisition proposal. Under the Merger Agreement, if the Williams Board changes the Williams Board Recommendation and the Merger Agreement is subsequently terminated, Williams would be required to pay a termination fee of up to $410 million to Williams Partners. This provision could discourage third parties that may have an interest in acquiring all or a significant part of Williams from considering or proposing that acquisition, or could result in a potential acquirer of Williams proposing to pay a lower price than it would otherwise have proposed to pay if the added expense of the termination fee was not payable. See “The Merger Agreement — Williams Board Recommendation; No Shop; and Williams Adverse Recommendation Change,” “The Merger Agreement — Termination.”

Tax Risks Related to the Merger and the Ownership of Williams Common Stock Received in the Merger

In addition to reading the following risk factors, you are urged to read “Material U.S. Federal Income Tax Consequences” for a more complete discussion of the expected U.S. federal income tax consequences of the Merger and owning and disposing of Williams Common Stock received in the Merger.

The Merger should be a taxable transaction and, in such case, the resulting tax liability of a WPZ Public Unitholder, if any, will depend on the unitholder’s particular situation. The tax liability of a WPZ Public Unitholder as a result of the Merger could be more than expected.

WPZ Public Unitholders will receive Williams Common Stock and cash in lieu of fractional shares, if any, as the Merger Consideration. Although WPZ Public Unitholders will receive no cash consideration other than any cash received in lieu of fractional shares, if any, the Merger should be treated as a taxable sale by WPZ Public Unitholders for U.S. federal income tax purposes. In such case, as a result of the Merger, a WPZ Public Unitholder will recognize gain or loss for U.S. federal income tax purposes equal to the difference between such unitholder’s amount realized and the unitholder’s adjusted tax basis in the WPZ Public Units. The amount of gain or loss recognized by each WPZ Public Unitholder in the Merger will vary depending on each unitholder’s particular situation, including the value of the shares of Williams Common Stock and the amount of cash in lieu of fractional shares, if any, received by each unitholder in the Merger, the adjusted tax basis of the WPZ Public Units exchanged by each unitholder in the Merger, and the amount of any suspended passive losses that may be available to a particular unitholder to offset a portion of the gain recognized by the unitholder.

Because the value of any Williams Common Stock received in the Merger will not be known until the effective time of the Merger, a WPZ Public Unitholder will not be able to determine its amount realized, and therefore its taxable gain or loss, until such time. In addition, because prior distributions in excess of a WPZ Public Unitholder’s allocable share of Williams Partners’ net taxable income decrease such WPZ Public Unitholder’s tax basis in its WPZ Public Units, the amount, if any, of such prior excess distributions with respect to such WPZ Public Units will, in effect, become taxable income to a WPZ Public Unitholder if the aggregate value of the consideration received in the Merger is greater than such WPZ Public Unitholder’s adjusted tax basis in its WPZ Public Units, even if the aggregate value of the consideration received in the Merger is less than such WPZ Public Unitholder’s original cost basis in its WPZ Public Units. Furthermore, a portion of this gain or loss, which portion could be substantial, will be separately computed and taxed as ordinary income or loss to the extent attributable to assets giving rise to depreciation recapture or other “unrealized receivables” or to “inventory items” owned by Williams Partners and its subsidiaries.

For a more complete discussion of certain U.S. federal income tax consequences of the Merger, please read “Material U.S. Federal Income Tax Consequences.”

The U.S. federal income tax treatment to WPZ Public Unitholders with respect to owning and disposing of any shares of Williams Common Stock received in the Merger will be different than their U.S. federal income tax treatment with respect to owning and disposing of their WPZ Public Units.

Williams Partners is classified as a partnership for U.S. federal income tax purposes and, generally, is not subject to entity-level U.S. federal income taxes. Instead, each WPZ Public Unitholder is required to take into

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account such unitholder’s share of items of income, gain, loss, and deduction of Williams Partners in computing its U.S. federal income tax liability, regardless of whether cash distributions are made to such WPZ Public Unitholder by Williams Partners. A distribution of cash by Williams Partners to a WPZ Public Unitholder who is a U.S. holder (as defined in the section titled “Material U.S. Federal Income Tax Consequences”) is generally not taxable for U.S. federal income tax purposes unless the amount of cash distributed is in excess of the WPZ Public Unitholder’s adjusted tax basis in its WPZ Public Units. In contrast, Williams is classified as a corporation for U.S. federal income tax purposes, and thus, Williams (and not its stockholders) is subject to U.S. federal income tax on its taxable income. A distribution of cash by Williams to a stockholder who is a U.S. holder will generally be included in such U.S. holder’s income as ordinary dividend income to the extent of Williams’ current or accumulated “earnings and profits,” as determined under U.S. federal income tax principles. A portion of the cash distributed to Williams Stockholders by Williams after the Merger may exceed Williams’ current and accumulated earnings and profits. Cash distributions in excess of Williams’ current and accumulated earnings and profits will be treated as a non-taxable return of capital, reducing a U.S. holder’s adjusted tax basis in such stockholder’s Williams Common Stock and, to the extent the cash distribution exceeds such stockholder’s adjusted tax basis, as gain from the sale or exchange of such shares of Williams Common Stock.

Please read “Material U.S. Federal Income Tax Consequences” for a more complete discussion of certain U.S. federal income tax consequences of owning and disposing of Williams Common Stock.

Williams’ future tax liability may be greater than expected if it does not generate net operating losses (“NOLs”) sufficient to offset taxable income or if tax authorities challenge certain of its tax positions.

Williams expects to generate deductions and NOL carryforwards that it can use to offset taxable income. As a result, Williams does not expect to pay meaningful U.S. federal income tax through at least 2024. This estimate is based upon assumptions Williams has made regarding, among other things, income, capital expenditures and net working capital. Further, the Internal Revenue Service (the “IRS”) or other tax authorities could challenge one or more tax positions Williams takes, such as the classification of assets under the income tax depreciation rules, the characterization of expenses for income tax purposes, and the tax classification of the Merger. Further, any change in law may affect Williams’s tax position. While Williams expects that its deductions and NOL carryforwards will be available to it as a future benefit, in the event that they are not generated as expected, are successfully challenged by the IRS (in a tax audit or otherwise) or are subject to future limitations, Williams’s ability to realize these benefits may be limited.

Risks Inherent in an Investment in Williams

The Williams Common Stock to be received by WPZ Public Unitholders as a result of the Merger has different rights from WPZ Units.

Following completion of the Merger, WPZ Public Unitholders will no longer hold WPZ Units, but will instead hold shares of Williams Common Stock. Williams is a corporation, and Williams Partners is a limited partnership. There are important differences between the rights of WPZ Unitholders and the rights of Williams Stockholders. See “Comparison of Rights of Williams Stockholders and WPZ Unitholders” for a discussion of the different rights associated with WPZ Units and Williams Common Stock.

If the Charter Amendment is approved, Williams will be able to issue more shares of Williams Common Stock than are expected to be outstanding immediately after the Merger is completed. Any future issuances of Williams Common Stock may have a dilutive effect on the earnings per share and voting power of Williams Stockholders.

The Charter Amendment authorizes a greater number of shares of Williams Common Stock than are expected to be outstanding immediately after the Merger is completed. If the Charter Amendment is approved, Williams will be able to issue more shares of Williams Common Stock than is expected to be outstanding

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immediately after the Merger is completed. If the Williams Board elects to issue additional shares of Williams Common Stock in the future, whether in public offerings, in connection with mergers and acquisitions or otherwise, such additional issuances may further dilute the earnings per share and voting power of the combined Williams Stockholders and may adversely affect the market price of the Williams Common Stock. If the Charter Amendment Proposal is approved by Williams Stockholders, the Charter Amendment will be effective even if the Merger does not take place.

Williams’ ability to pay dividends is restricted by Delaware law.

Under the General Corporation Law of the State of Delaware (the “DGCL”), the Williams Board may not authorize payment of a dividend unless it is either paid out of surplus, as calculated in accordance with the DGCL, or if Williams does not have a surplus, it is paid out of net profits for the fiscal year in which the dividend is declared and/or the preceding fiscal year. Williams’ by-laws require the declaration and payment of dividends to comply with the DGCL. If, as a result of these restrictions, Williams is unable to authorize payment of dividends, a decline in the market price or liquidity, or both, of the Williams Common Stock could result. This may in turn result in losses by Williams Stockholders.

Restrictions in Williams’ and Williams Partners’ debt agreements and the amount of Williams and Williams Partners’ indebtedness may affect Williams’ future financial and operating flexibility.

Williams had approximately $4.3 billion total outstanding long-term debt (including current portion), and Williams Partners had approximately $17.0 billion total outstanding long-term debt (including current portion), as of June 29, 2018. As of June 29, 2018, Williams Partners had no commercial paper outstanding under its commercial paper program. Following the closing of the Merger, it is expected that Williams Partners will merge with and into Williams, thereby causing Williams to become liable for the debt of Williams Partners. The indebtedness of the subsidiaries of Williams Partners will be unaffected by the Merger. Further, in connection with the Post-Closing Merger, Williams expects to amend and restate its existing credit facility, or enter into a new credit facility, in each case on terms that are yet to be determined (the “New Williams Credit Facility”).

The agreements governing Williams’ and Williams Partners’ indebtedness contain covenants that restrict Williams’, Williams Partners’, and their respective material subsidiaries’ ability to incur certain liens to support indebtedness and Williams’ and Williams Partners’ ability to merge or consolidate or sell all or substantially all of their respective assets in certain circumstances. In addition, certain of Williams’ and Williams Partners’ debt agreements contain various covenants that restrict or limit, among other things, their respective ability to make certain distributions during the continuation of an event of default, the ability of their respective subsidiaries to incur additional debt, and Williams’, Williams Partners’, and their respective material subsidiaries’ ability to enter into certain affiliate transactions and certain restrictive agreements. Certain of Williams’ and Williams Partners’ debt agreements also contain, the New Williams Credit Facility will contain, and those other debt agreements Williams may enter into in the future may contain, financial covenants and other limitations with which Williams and its subsidiaries will need to comply.

Williams’ and Williams Partners’ debt service obligations and the covenants described above could have important consequences. For example, they could:

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Williams’ and Williams Partners’ ability to comply with their respective debt covenants, to repay, extend or refinance their respective existing debt obligations (including the debt of Williams Partners for which Williams will become liable following the Post-Closing Merger) and to obtain future credit will depend primarily on their respective operating performances. Williams’ ability to refinance its and Williams Partners’ existing debt obligations or obtain future credit will also depend upon the current conditions in the credit markets and the availability of credit generally. If Williams or Williams Partners are unable to comply with their respective debt covenants, meet their respective debt service obligations or obtain future credit on favorable terms, or at all, Williams and Williams Partners could be forced to restructure or refinance their respective indebtedness, seek additional equity capital or sell assets. Williams and/or Williams Partners may be unable to obtain financing or sell assets on satisfactory terms, or at all.

Williams’ or Williams Partners’ failure to comply with the covenants in the documents governing their respective indebtedness could result in events of default, which could render such indebtedness due and payable. Williams or Williams Partners may not have sufficient liquidity to repay such indebtedness in such circumstances. In addition, cross-default or cross-acceleration provisions in Williams’ and Williams Partners’ debt agreements could cause a default or acceleration to have a wider impact on its liquidity than might otherwise arise from a default or acceleration of a single debt instrument.

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WRITTEN CONSENTS OF HOLDERS OF WPZ UNITS

WPZ Units Entitled to Consent and Consent Required

Only WPZ Unitholders of record at the close of business on the WPZ Record Date of July 9, 2018 will be notified of and be entitled to execute and deliver a written consent with respect to the Merger Agreement and the Merger. The approval and adoption of the Merger Agreement and the Merger by Williams Partners requires the affirmative vote or consent of holders of a majority of the outstanding WPZ Units.

Pursuant to the terms of the Support Agreement, Williams Gas Pipeline, which as of May 15, 2018 beneficially owned 702,218,502 WPZ Common Units and 18,442,649 WPZ Class B Units representing approximately 73.8% of the outstanding WPZ Units, has irrevocably agreed to deliver the WGP Written Consent adopting and approving in all respects the Merger Agreement and the transactions contemplated thereby, including the Merger, within two business days after the effectiveness of the registration statement of which this joint consent statement/proxy statement/prospectus forms a part. The delivery of the WGP Written Consent by Williams Gas Pipeline with respect to the WPZ Units it owns will be sufficient to approve the Merger Agreement and the Merger on behalf of Williams Partners.

Submission of Consents

Holders of WPZ Units may consent to the approval and adoption of the Merger Agreement and the Merger with respect to their WPZ Units by completing, dating and signing the written consent furnished with this joint consent statement/proxy statement/prospectus and returning it to Williams Partners.

If you are a WPZ Unitholder of record at the close of business on the WPZ Record Date and you wish to give your written consent, you must fill out the enclosed written consent, date and sign it, and promptly return it to Williams Partners by following the instructions in the next sentence. Once you have completed, dated and signed the written consent, you may deliver it to Williams Partners by faxing it to Williams Partners L.P., Attention: Secretary, at 918-573-1807, by emailing a .pdf copy of your written consent to WPZMergerVote@williams.com or by mailing your written consent to Williams Partners L.P. at One Williams Center, Tulsa, Oklahoma 74172-0172, Attention: Secretary. If you do not return your written consent, it will have the same effect as a vote against the approval and adoption of the Merger Agreement and the transactions contemplated thereby, including the Merger.

Once a sufficient number of consents to approve and adopt the Merger Agreement and the transactions contemplated thereby, including the Merger, have been received, the consent process will conclude. The delivery of the WGP Written Consent with respect to the WPZ Units owned by Williams Gas Pipeline approving the Merger Agreement will be sufficient to approve the Merger Agreement and the Merger on behalf of Williams Partners.

Revocation of Consents

Your consent may be revoked at any time before the consents of a sufficient number of WPZ Units to approve the adoption of the Merger Agreement and the transactions contemplated thereby, including the Merger, have been delivered to the secretary of Williams Partners. If you wish to revoke a previously given consent before that time, you may do so by faxing such revocation to Williams Partners L.P., Attention: Secretary, at 918-573-1807, by emailing a .pdf copy of such revocation to WPZMergerVote@williams.com or by mailing such revocation to Williams Partners L.P. at One Williams Center, Tulsa, Oklahoma 74172-0172, Attention: Secretary.

Expenses

The expense of printing and mailing these consent materials to WPZ Public Unitholders is being borne by Williams Partners.

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THE WILLIAMS SPECIAL MEETING OF STOCKHOLDERS

Williams is providing this joint consent statement/proxy statement/prospectus to the Williams Stockholders in connection with the solicitation of proxies to be voted at the Williams Special Meeting that Williams has called for the purposes described below. This joint consent statement/proxy statement/prospectus is first being mailed to Williams Stockholders on or about July 12, 2018 and provides the Williams Stockholders with the information they need to know about the Merger and the proposals to be able to vote or instruct their vote to be cast at the Williams Special Meeting.

Date, Time and Place

The Williams Special Meeting will be held on August 9, 2018 at 10:00 a.m., local time, at One Williams Center, Tulsa, Oklahoma 74172-0172.

Purpose; Proposals

At the Williams Special Meeting, you will be asked to consider and vote on the following proposals:

Proposal 1: to adopt an amendment to the Williams certificate of incorporation to increase the number of authorized shares of capital stock from 990,000,000 shares to 1,500,000,000 shares, consisting of 1,470,000,000 shares of Williams Common Stock and 30,000,000 shares of Williams preferred stock, par value $1.00 per share;

Proposal 2: to approve, subject to and conditioned upon the effectiveness of the Charter Amendment, the issuance of Williams Common Stock in the Merger pursuant to the Merger Agreement; and

Proposal 3: to approve the adjournment of the Williams Special Meeting, if necessary or appropriate to solicit additional proxies if there are insufficient votes at the time of the Williams Special Meeting to approve the Charter Amendment Proposal or the Stock Issuance Proposal.

Board Recommendation

The Williams Board recommends that Williams Stockholders vote “FOR” each of the Proposals. See the section titled “Recommendation of the Williams Board and Its Reasons for the Merger.”

In considering the recommendation of the Williams Board with respect to the proposals, you should be aware that some of Williams’ directors and executive officers may have interests that are different from, or in addition to, the interests of Williams Stockholders more generally. See the section titled “The Merger - Interests of Certain Persons in the Merger.”

Record Date; Outstanding Shares; Shares Entitled to Vote

Only Williams Stockholders of record as of the close of business on the Williams Vote Record Date will be entitled to receive notice of and to vote at the Williams Special Meeting or at any adjournment or postponement of the meeting. Williams Common Stock held by Williams as treasury shares will not be entitled to vote.

As of the close of business on the Williams Vote Record Date, there were 827,957,583 shares of Williams Common Stock and no other shares of capital stock outstanding and entitled to vote at the meeting. Each Williams Stockholder is entitled to one vote for each share of Williams Common Stock owned as of the Williams Vote Record Date.

A complete list of Williams Stockholders entitled to vote at the Williams Special Meeting will be available for inspection at Williams’ principal place of business during regular business hours for a period of no less than ten days before the Williams Special Meeting and, during the Williams Special Meeting, at One Williams Center, Tulsa, Oklahoma 74172-0172.

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Quorum

A quorum of Williams Stockholders is required to approve the Charter Amendment Proposal and the Stock Issuance Proposal at the Williams Special Meeting, but not to approve any Adjournment Proposal. A majority of the outstanding shares of Williams Common Stock as of the Williams Vote Record Date must be represented in person or by proxy at the Williams Special Meeting in order to constitute a quorum.

Required Vote

The approval of the Charter Amendment Proposal requires the affirmative vote of holders of a majority of the outstanding shares of Williams Common Stock entitled to vote thereon. As a result, if you do not vote your shares of Williams Common Stock or abstain from voting, it will have the same effect as a vote against the Charter Amendment Proposal.

The approval of the Stock Issuance Proposal requires the affirmative vote of a majority of the votes cast on such proposal at the Williams Special Meeting, provided a quorum is present. The approval of the Adjournment Proposal requires the affirmative vote of a majority of the votes cast on such proposal at the Williams Special Meeting, regardless of whether a quorum is present. Abstentions will be counted as votes cast for purposes of the Stock Issuance Proposal, but will not be treated as votes cast for purposes of the Adjournment Proposal. As a result, if you abstain from voting on the Stock Issuance Proposal, your Williams Common Stock will be counted as present for purposes of establishing a quorum, but the abstention will have the same effect as a vote against that proposal. If you abstain from voting on the Adjournment Proposal, your Williams Common Stock will be disregarded for purposes of determining the votes cast for the Adjournment Proposal, and the abstention will therefore have no effect on the adoption of that proposal. If you fail to vote on the Stock Issuance Proposal or the Adjournment Proposal, such failure to vote will not affect the adoption of such proposal, except with respect to the Stock Issuance Proposal to the extent that your failure to vote prevents the establishment of a quorum at the Williams Special Meeting.

The obligations of the parties to complete the Merger are conditioned upon approval of each of the Charter Amendment Proposal and the Stock Issuance Proposal. Accordingly, a vote against or an abstention with respect to the Charter Amendment Proposal or the Stock Issuance Proposal, or a failure to vote on the Stock Issuance Proposal, to the extent such failure prevents a quorum from forming, will have the same effect as a vote against the Merger (although no vote for or against the Merger is taking place). If the Charter Amendment Proposal is approved by Williams Stockholders, the Charter Amendment will be effective even if the Merger does not take place.

Stock Ownership of and Voting of Williams’ Directors and Executive Officers

As of the Williams Vote Record Date, Williams’ directors and executive officers beneficially owned and were entitled to vote, in the aggregate, approximately 0.07% of the outstanding Williams Common Stock.

Voting and Submitting a Proxy for Williams Common Stock Held by Holders of Record

If you were a holder of record of Williams Common Stock at the close of business on the Williams Vote Record Date, you may vote in person by attending the Williams Special Meeting or, to ensure that your shares are represented at the Williams Special Meeting, you may authorize a proxy to vote by:

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When you submit a proxy by telephone or via the Internet, your proxy is recorded immediately. We encourage you to submit your proxy using these methods whenever possible. If you submit a proxy by telephone or via the Internet, please do not return your proxy card by mail.

All shares of Williams Common Stock represented by each properly executed and valid proxy received before the Williams Special Meeting will be voted in accordance with the instructions given on the proxy. If a Williams Stockholder executes a proxy card without giving instructions, the Williams Common Stock represented by that proxy card will be voted “FOR” each of the Proposals.

Your vote is important. Accordingly, please submit your proxy by telephone, via the Internet, or by mail whether or not you plan to attend the meeting in person. Proxies must be received by 11:59 p.m., Central Time, on August 8, 2018.

Voting and Submitting a Proxy for Williams Common Stock Held in Street Name

If your Williams Common Stock is held in an account at a bank, broker, or other nominee, you must instruct the bank, broker, or other nominee on how to vote them by following the instructions that the bank, broker, or other nominee provides to you with these proxy materials. Most banks, brokers, and other nominees offer the ability for stockholders to submit voting instructions by mail by completing a voting instruction card, by telephone, and via the Internet.

If you hold your Williams Common Stock in a brokerage account and you do not provide voting instructions to your broker, your shares will not be voted on any Proposal because under the current rules of the NYSE brokers do not have discretionary authority to vote on the Proposals. Since there are no items on the agenda that your broker has discretionary authority to vote upon, broker non-votes will not be counted as present at the meeting if you fail to instruct your brokerage firm on how to vote on any of the Proposals. Therefore, a broker non-vote will have the same effect as a vote against the Charter Amendment Proposal, but will have no effect on the Stock Issuance Proposal or the Adjournment Proposal, except with respect to the Stock Issuance Proposal to the extent such broker non-vote prevents the establishment of a quorum at the Williams Special Meeting.

If you hold shares through a bank, broker, or other nominee and wish to vote your shares in person at the Williams Special Meeting, you must obtain a legal proxy from your bank, broker, or other nominee and present it to the inspector of election with your ballot when you vote at the Williams Special Meeting.

If you hold shares in The Williams Investment Plus Plan, you may direct the trustee of the plan how to vote your plan shares by calling the toll-free number shown on your proxy card, voting on the Internet on the website shown on the proxy card, or completing and returning the enclosed proxy card in the postage-paid envelope. Please note, in order to permit the trustee to tally and vote all shares of Williams Common Stock held in The Williams Investment Plus Plan, your instructions, whether by Internet, by telephone, or by proxy card, must be completed prior to 1:00 a.m. Central Daylight Time on August 6, 2018. You may not change your vote related to such plan shares after this deadline. If you do not instruct the trustee how to vote, your plan shares will be voted by the trustee in the same proportion that it votes shares in other plan accounts for which it did receive timely voting instructions. The proportional voting policy is detailed under the terms of the plan and the trust agreement.

Revocability of Proxies; Changing Your Voting Instructions

If you are a stockholder of record, you may revoke your proxy and/or change your voting instructions by:

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If you choose to revoke your proxy by written notice or submit a later-dated proxy, you must do so by 11:59 p.m., Central Time, on August 8, 2018.

If you hold your Williams Common Stock in street name through a bank, broker, or other nominee, you must follow the directions you receive from such bank, broker, or other nominee to revoke or change your vote.

Solicitation of Proxies

Williams will bear all costs and expenses in connection with the solicitation of proxies from its stockholders. Williams has engaged Okapi to assist in the solicitation of proxies for the Williams Special Meeting and Williams estimates that it will pay Okapi a base fee of approximately $15,000 plus reasonable expenses for its services in connection with the Merger. Williams has also agreed to reimburse Okapi for reasonable out-of-pocket expenses and disbursements incurred in connection with the proxy solicitation, such as phone calls with Williams Stockholders. These expenses and disbursements could be substantial. Williams has agreed to indemnify Okapi against certain losses, costs, and expenses. In addition, Williams will reimburse brokerage firms and other persons representing beneficial owners of Williams Common Stock for their reasonable expenses in forwarding solicitation materials to such beneficial owners. Proxies also may be solicited by certain of Williams’ directors, officers and employees by telephone, electronic mail, letter, facsimile, or in person, but no additional compensation will be paid to them.

No Other Business

No business shall be conducted at the Williams Special Meeting other than the matters described herein.

Adjournments

Adjournments may be made for the purpose of, among other things, soliciting additional proxies. If there are insufficient votes at the Williams Special Meeting to approve and adopt the Charter Amendment Proposal or approve the Stock Issuance Proposal and it is necessary or appropriate to solicit additional proxies, the Williams Special Meeting may be adjourned. If a quorum is not present, an adjournment may be made from time to time by the chairman of the meeting or by the affirmative vote of holders of a majority of the shares of Williams Stockholders entitled to vote at the meeting, present in person or by proxy. Whether or not a quorum is present, an adjournment may be made from time to time by the affirmative vote of holders of a majority of the shares of Williams Stockholders entitled to vote at the meeting, present in person or by proxy. Williams is not required to notify Williams Stockholders of any adjournment of 30 days or less if the time and place of the adjourned meeting are announced at the meeting at which such adjournment is taken, unless after the adjournment a new record date is fixed for the adjourned meeting. At any adjourned meeting, Williams may transact any business that it might have transacted at the original meeting, provided that a quorum is present at such adjourned meeting. Proxies submitted by Williams Stockholders for use at the Williams Special Meeting will be used at any adjournment or postponement of the Williams Special Meeting. References to the Williams Special Meeting in this joint consent statement/proxy statement/prospectus are to such Williams Special Meeting as adjourned or postponed.

Attending the Williams Special Meeting

All Williams Stockholders as of the close of business on the Williams Vote Record Date, or their duly appointed proxies, may attend the Williams Special Meeting. Registration will begin on the date of the Williams Special Meeting at 9:30 a.m. local time. Cameras, recording devices, and other electronic devices will not be permitted at the Williams Special Meeting.

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Williams Stockholders and proxies will be asked to present valid picture identification, such as a driver’s license or passport. If you hold your shares in street name, you will also need to bring a copy of the voting instruction card you receive from your bank, broker, or other nominee in connection with the Williams Special Meeting or a brokerage statement reflecting your Williams Common Stock ownership as of the close of business on the Williams Vote Record Date and check in at the registration desk at the Williams Special Meeting.

Assistance

If you need assistance in completing your proxy card, have questions regarding the Williams Special Meeting, or would like additional copies, without charge, of this document, please contact Okapi by phone at (888) 785-6617 or email at williamsinfo@okapipartners.com.

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THE MERGER

General

On May 16, 2018, Williams, Merger Sub, Williams Partners, and WPZ General Partner entered into the Merger Agreement pursuant to which Merger Sub will merge with and into Williams Partners, with Williams Partners surviving as a wholly owned subsidiary of Williams.

Pursuant to the Merger Agreement, each WPZ Public Unit will be converted into the right to receive a number of shares of Williams Common Stock equal to the Exchange Ratio and each such WPZ Public Unit will be canceled and retired and will cease to exist. No fractional shares of Williams Common Stock will be issued in the Merger, and holders of WPZ Public Units will, instead, receive cash in lieu of such fractional shares, if any.

The approval and adoption of the Merger Agreement and the Merger by Williams Partners requires the affirmative vote or consent of holders of a majority of the outstanding WPZ Units. Pursuant to the terms of the Support Agreement, Williams Gas Pipeline, which as of May 15, 2018 beneficially owned 702,218,502 WPZ Common Units and 18,442,649 WPZ Class B Units representing approximately 73.8% of the outstanding WPZ Units, has irrevocably agreed to deliver the WGP Written Consent adopting and approving in all respects the Merger Agreement and the transactions contemplated thereby, including the Merger, within two business days after the effectiveness of the registration statement of which this joint consent statement/proxy statement/prospectus forms a part. The delivery of the WGP Written Consent by Williams Gas Pipeline with respect to the WPZ Units it owns will be sufficient to approve the Merger Agreement and the Merger on behalf of Williams Partners.

As a condition to the Closing, the Williams Stockholders must approve the adoption of the Charter Amendment and approve the Stock Issuance at the Williams Special Meeting. The approval of the adoption of the Charter Amendment requires the affirmative vote of holders of a majority of the outstanding Williams Common Stock entitled to vote thereon. The approval of the Stock Issuance requires the affirmative vote of a majority of the votes cast on the Stock Issuance Proposal at the Williams Special Meeting, provided a quorum is present. If the Charter Amendment Proposal is approved by Williams Stockholders, the Charter Amendment will be effective even if the Merger does not take place.

Williams’ Ownership Interest In and Control of Williams Partners

WPZ Public Unitholders should be aware that Williams Partners is controlled by Williams through Williams’ 100% ownership of the WPZ General Partner. The WPZ General Partner owns all of the outstanding general partner interests in Williams Partners. As a result, Williams appoints the members of the WPZ Board, a majority of whom are affiliated with Williams and its affiliates, and thereby could be seen as controlling all of Williams Partners’ decisions, other than those involving certain conflicts of interest with Williams or that require an affirmative vote of holders of the limited partner interests in Williams Partners pursuant to and in the percentages specified by the Williams Partners partnership agreement. In addition, Williams, through its ownership of Williams Gas Pipeline, owns an approximate 73.8% limited partner interest in Williams Partners.

Certain persons associated with Williams have a relationship with Williams Partners.

Alan S. Armstrong, who serves as Chairman of the Board and Chief Executive Officer of the WPZ General Partner, also serves as a director, executive officer, and/or member of the management committee of certain affiliates of the WPZ General Partner, including Williams. Micheal G. Dunn, who serves as a director and Chief Operating Officer of the WPZ General Partner, also serves as a director, executive officer, and/or member of the management committee of certain affiliates of the WPZ General Partner, including Williams. John D. Chandler, who serves as a director and the Chief Financial Officer of the WPZ General Partner, also serves as a director, executive officer, and/or member of the management committee of certain affiliates of the WPZ General Partner, including Williams. Walter J. Bennett serves as Senior Vice President — West of each of the WPZ General Partner and Williams. Chad J. Zamarin, who serves as a director and Senior Vice President — Corporate

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Strategic Development of the WPZ General Partner, also serves as the Senior Vice President — Corporate Strategic Development of Williams. Frank J. Ferazzi, who serves as Senior Vice President — Atlantic—Gulf of the WPZ General Partner, also serves as the Senior Vice President — Atlantic—Gulf of Williams. T. Lane Wilson, who serves as Senior Vice President and General Counsel of Williams, also serves as the Senior Vice President and General Counsel of the WPZ General Partner. John E. Poarch serves as Senior Vice President — Engineering Services of each of the WPZ General Partner and Williams. James E. Scheel serves as Senior Vice President — Northeast G&P of each of the WPZ General Partner and Williams. Ted T. Timmermans serves as Vice President, Controller, and Chief Accounting Officer of each of the WPZ General Partner and Williams.

Background of the Merger

The senior management of Williams and the Williams Board regularly review operational and strategic opportunities to maximize value for investors of Williams. The senior management of Williams Partners and the WPZ Board regularly review operational and strategic opportunities to maximize value for investors of Williams Partners. In connection with these reviews, the respective management and boards of directors of Williams and Williams Partners from time to time evaluate potential transactions that would further their respective strategic objectives.

On May 12, 2015, Williams and Williams Partners entered into an agreement and plan of merger (the “2015 WPZ Merger Agreement”) pursuant to which Williams agreed to acquire all of the outstanding WPZ Public Units in an all stock-for-unit transaction (the “Proposed 2015 WPZ Merger”). On May 19, 2015, Williams received an unsolicited proposal from Energy Transfer Equity, L.P. (“ETE”) regarding a potential acquisition by an affiliate of ETE of 100% of the outstanding shares of Williams Common Stock (the “2015 ETE Proposal”). The 2015 ETE Proposal was conditioned upon the termination by Williams of the 2015 WPZ Merger Agreement. Following extensive separate negotiations with ETE and the WPZ Conflicts Committee, on September 28, 2015, Williams entered into a merger agreement with ETE (the “ETE Merger Agreement”) and terminated the 2015 WPZ Merger Agreement. In connection with such termination, Williams paid a termination fee to Williams Partners in the amount of $428 million. On June 29, 2016, ETE sent a notice of termination under the ETE Merger Agreement.

On January 9, 2017, following extensive negotiations between Williams and the WPZ Conflicts Committee, Williams and Williams Partners consummated a series of transactions designed to simplify the Williams Partners capital structure, which included the issuance by Williams Partners to Williams Gas Pipeline of 289,000,000 newly issued WPZ Common Units in exchange for (i) the permanent waiver by Williams of its incentive distribution rights under the Williams Partners partnership agreement and (ii) the conversion of the WPZ General Partner’s economic general partner interest to a non-economic general partner interest.

On March 15, 2018, the Federal Energy Regulatory Commission (the “FERC”) issued orders aimed at addressing recovery of income tax costs in the regulated rates charged by master limited partnership pipelines, including a reversal on its 2005 policy of allowing master limited partnership pipelines to include an income-tax allowance in their cost-of-service (the “FERC Announcement”). The trading price of the Williams Common Stock and the WPZ Common Units reacted negatively to the FERC Announcement, including the Williams Common Stock closing five percent lower the day of the FERC Announcement and closing over twelve percent lower during the three weeks following the FERC Announcement, in each case as compared to the closing price of the Williams Common Stock on the trading day immediately preceding the date of the FERC Announcement.

On March 15, 2018, following the FERC Announcement, Mr. John D. Chandler, the Chief Financial Officer of Williams and the WPZ General Partner, contacted Morgan Stanley, financial advisor to Williams, and asked Morgan Stanley to begin evaluating options to address and mitigate the potential financial consequences to Williams and Williams Partners of the FERC Announcement, including a potential combination of Williams and Williams Partners.

On March 23, 2018, the WPZ Board held a telephonic meeting during which it discussed both the financial impact of the FERC Announcement on Williams Partners and possible alternative approaches to mitigate the

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impact of the FERC Announcement, including a potential transaction involving the acquisition by Williams of the WPZ Public Units. At the meeting, members of Williams management informed the members of the WPZ Conflicts Committee, comprised of Mr. H. Brent Austin (Chairman), Mr. Philip L. Frederickson and Ms. Alice M. Peterson, that some of the options being considered by Williams management in response to the FERC Announcement could require approval by the WPZ Conflicts Committee, and therefore the WPZ Conflicts Committee should consider engaging legal and financial advisors to evaluate any such potential transaction.

Following the meeting, Mr. Austin, on behalf of the WPZ Conflicts Committee, contacted representatives of Baker Botts L.L.P. (“Baker Botts”) to discuss engaging Baker Botts as legal counsel to represent the WPZ Conflicts Committee in connection with considering various alternatives, including a potential transaction involving the acquisition by Williams of the WPZ Public Units. The WPZ Conflicts Committee engaged Baker Botts because of Baker Botts’ knowledge, expertise and experience with respect to public merger and acquisition transactions and conflicts committee engagements and because of Baker Botts’ performance during prior representations of the WPZ Conflicts Committee, specifically, through numerous prior drop-down transactions, the prior merger between ACMP and Williams Partners in 2014 (the “ACMP Merger”), the Proposed 2015 WPZ Merger and the Financial Repositioning in 2017.

On April 6, 2018, Mr. Austin contacted representatives of Evercore on behalf of the WPZ Conflicts Committee to discuss engaging Evercore because of Evercore’s knowledge and experience with respect to public merger and acquisition transactions, particularly transactions involving MLPs, and Evercore’s experience with Williams Partners, through its role as financial advisor to the conflicts committee of the board of directors of ACMP’s general partner in the ACMP Merger and prior engagement as the financial advisor to the WPZ Conflicts Committee in the Proposed 2015 WPZ Merger. An engagement letter detailing the terms of Evercore’s engagement was executed on April 11, 2018, after the WPZ Conflicts Committee, with Baker Botts’ assistance, had reviewed and negotiated acceptable terms thereof.

Later that day, Mr. Chandler sent an email to representatives of Evercore and Mr. Austin providing operational and financial updates and an updated forecast with respect to Williams Partners, as well as analysis outlining the potential financial impact of the FERC Announcement on Williams Partners and its subsidiaries. Mr. Chandler subsequently participated in teleconferences with representatives from Evercore to discuss the materials he provided.

On April 9, 2018, the WPZ Conflicts Committee engaged Richards, Layton & Finger P.A. (“RLF”) as Delaware counsel.

On April 12, 2018, the Williams Board held a telephonic meeting. At the meeting, members of Williams management discussed with the Williams Board various possible approaches to responding to and addressing the FERC Announcement, including challenging the FERC Announcement, making an election to have certain subsidiaries of Williams Partners be taxed as corporations, and potential taxable and nontaxable transactions involving the acquisition by Williams of the WPZ Public Units. Representatives from Morgan Stanley provided analyses regarding possible responses to the FERC Announcement. The Williams Board took no action at such meeting with respect to any potential responses to the FERC Announcement.

Later that day, Mr. Chandler sent an email to representatives of Evercore containing tax analysis with respect to a potential transaction with Williams Partners. Representatives of Evercore responded to Mr. Chandler and requested certain due diligence materials needed for Evercore’s analysis with respect to such potential transaction.

On April 14, 2018, Mr. Chandler participated in a teleconference with Mr. Austin, during which Mr. Chandler outlined a framework for a potential transaction involving the acquisition by Williams of the WPZ Public Units. Mr. Chandler noted that the Williams Board had not given any authorization or taken any action regarding a transaction with Williams Partners, including the framework outlined by Mr. Chandler, and that any

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transaction would be subject to the support and approval of the Williams Board. Mr. Chandler summarized the relative trading performance of the Williams Common Stock and WPZ Common Units subsequent to the FERC Announcement. Mr. Chandler noted that based on the recent trading history of the Williams Common Stock and the WPZ Common Units, Williams management believed an exchange ratio of 1.384 shares of Williams Common Stock for each WPZ Public Unit (i.e., 1.384x) would be appropriate, which represented a 0% premium to the exchange ratio based on closing prices of the Williams Common Stock and the WPZ Common Units on April 12, 2018, or a 6.2% premium to the exchange ratio based on 10-day volume weighted prices through the day of the FERC Announcement on March 15, 2018 (such exchange ratio to be referred to as the “Unaffected VWAP Exchange Ratio”). Mr. Chandler also noted that, based on the timing of payments of the Williams and Williams Partners respective regular quarterly dividends/distributions, the WPZ Public Unitholders would potentially be entitled to receive a dividend/distribution from both Williams and Williams Partners during the third quarter. Mr. Chandler and Mr. Austin also discussed the expected tax impacts of such potential transaction for the WPZ Public Unitholders, as well as the expected effect of such transaction on Williams’ credit rating. Following the call, Mr. Chandler sent a summary of illustrative terms of a potential transaction to members of the WPZ Conflicts Committee and representatives of Morgan Stanley sent the summary to representatives of Evercore.

On April 16, 2018, Mr. Chandler participated in a teleconference with representatives from Evercore regarding due diligence matters and the expected effect of a potential transaction on Williams’ credit rating. Subsequently, members of Williams management and representatives of Morgan Stanley participated in a teleconference with representatives of Evercore and Baker Botts to discuss and answer questions regarding the analysis that Williams management had previously provided regarding the overall effect and expected impact on Williams and Williams Partners of the FERC Announcement. In particular, the participants discussed the anticipated consequences of the FERC Announcement on Northwest Pipeline’s and Transco’s cost of service and revenues and anticipated impacts of Williams Partners’ remaining as a standalone partnership, as opposed to becoming a wholly owned subsidiary of Williams.

Later that afternoon, Mr. Chandler participated in a teleconference with Mr. Austin to discuss a potential transaction and available alternative transactions, including structuring alternatives that would result in a transaction that was not taxable to the WPZ Public Unitholders. Mr. Chandler noted that Williams management was continuing to evaluate all available structural alternatives to address the FERC Announcement, including both tax free and taxable merger structures, as well as the possibility of making an election to have certain subsidiaries of Williams Partners be taxed as corporations without any transaction with Williams.

On April 17, 2018, the WPZ Conflicts Committee participated in a teleconference with representatives of Baker Botts, including its tax specialists, and Evercore to discuss preliminary steps with respect to a potential transaction (among various alternatives being considered), including the process for evaluating financial models from Williams management and for analyzing the expected tax impacts of the potential transaction on the WPZ Public Unitholders. During the meeting, representatives of Baker Botts delivered a presentation to the WPZ Conflicts Committee to review the process by which the WPZ Board would authorize the WPZ Conflicts Committee to evaluate a potential transaction. Representatives of Baker Botts also explained the directors’ duties in, and best practices for, carrying out their evaluation, negotiations and review process. Joshua Davidson of Baker Botts previewed for the WPZ Conflicts Committee that members of Baker Botts’ tax and regulatory practice groups would help to review and evaluate the potential transaction throughout the evaluation and negotiation process and would be available to present to the WPZ Conflicts Committee their analyses of the potential transaction in subsequent WPZ Conflicts Committee meetings.

The participants also discussed the financial aspects of the potential transaction, including Evercore’s initial analysis of the preliminary forecasts presented by Williams and Williams Partners management to Evercore and certain aspects of Evercore’s preliminary views with respect to the potential transaction. Evercore provided an overview of the terms of the potential transaction and the exchange ratio suggested by Williams management. Evercore then provided an overview of the situation analyses and initial financial projections received for each of

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Williams and Williams Partners, and the meeting participants discussed the potential tax impacts of a potential transaction on the WPZ Public Unitholders across a wide array of tax classifications.

On April 18, 2018, the WPZ Board adopted resolutions by unanimous written consent formally delegating authority to the WPZ Conflicts Committee to review, evaluate and negotiate a potential transaction with Williams, without authorizing any particular approach, for the purpose of providing, if appropriate and if approved by both parties, “Special Approval” pursuant to Section 7.9(a) of the Williams Partners partnership agreement and to evaluate the terms and conditions, and determine the advisability, of such a transaction. Such authorization also ratified any actions previously taken by the WPZ Conflicts Committee in connection with the process.

Later that day, the WPZ Conflicts Committee participated in a teleconference with representatives of Baker Botts, including its tax and regulatory specialists, to discuss in greater detail the FERC Announcement and better understand the manner in which the WPZ Conflicts Committee should consider the potential impact to WPZ in remaining as a standalone partnership as opposed to potentially becoming a wholly owned subsidiary of Williams. Following the meeting, Evercore and Baker Botts began their preliminary financial and legal analyses, respectively, and due diligence review.

Also on April 18, 2018, members of Williams management participated in a teleconference with representatives from Evercore to provide operational and financial updates regarding Williams and Williams Partners, as well as to discuss potential changes to the Williams and Williams Partners financial forecasts arising from the FERC Announcement.

On April 20, 2018, Mr. Chandler sent to representatives from Morgan Stanley and Evercore revised financial projections for Williams and Williams Partners reflecting the potential impact of the FERC Announcement, which would result in an expected reduction to annual EBITDA of approximately $165 million starting in 2019 for Transco and Northwest Pipeline, collectively, as subsidiaries of Williams Partners compared to what they would generate as subsidiaries of Williams due to the lower recourse rates they would be able to charge as a result of FERC’s revised policy.

Later that day, representatives of Baker Botts sent a legal due diligence request list to Williams enumerating the various materials requested in connection with its review and evaluation of a potential transaction. Evercore and Baker Botts continued their ongoing financial and legal analyses, respectively, and due diligence review of a potential transaction.

On April 26, 2018, the WPZ Conflicts Committee held a teleconference with representatives of Baker Botts and Evercore to receive Evercore’s updated financial analysis and presentation. In particular, the Evercore team presented its additional analysis based on updated financial projections received from Williams management on April 25 and 26, 2018, in response to due diligence requests. Evercore’s updated presentation primarily updated the implied premium of the exchange ratio under consideration to the closing price from April 24, 2018, to reflect the updated financial projections. Evercore presented its preliminary valuation methodologies, including a discounted distribution/dividend analysis, peer group trading analysis and precedent M&A transaction analysis for each of Williams Partners and Williams. The WPZ Conflicts Committee members discussed the financial analysis Evercore presented and determined that an exchange ratio higher than 1.384x was justified. Mr. Davidson noted that Baker Botts had requested from Gibson Dunn, but not yet received, access to the electronic data room or initial drafts of the transaction documents, including the merger agreement. The WPZ Conflicts Committee agreed to wait to respond until Baker Botts had sufficient opportunity to review items responsive to its legal due diligence request. The WPZ Conflicts Committee took no action at this meeting with respect to a transaction.

On May 1, 2018, the WPZ Conflicts Committee held a teleconference with representatives of Baker Botts and Evercore to receive Evercore’s presentation and analysis of potential alternative transactions to the

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transaction under discussion. The potential alternatives included the possibility of (i) adding entities within the Williams Partners organizational structure that would be taxed as a corporation for United States income tax purposes and putting the Williams Partners regulated subsidiaries into such a subsidiary to continue to maintain the FERC income tax allowance in their cost-of-service rates (the “Blocker Structure”), (ii) selling the Williams Partners regulated subsidiaries or (iii) some combination of the foregoing. Evercore discussed the advantages and disadvantages of each of the alternatives and noted that each would likely allow Williams Partners to avoid the impact of the FERC Announcement on cost-of-service pipeline rates. After the discussions, the WPZ Conflicts Committee authorized Mr. Austin to contact Mr. Chandler to relay the WPZ Conflicts Committee’s interest in discussing potential alternatives to an acquisition by Williams of the WPZ Public Units, particularly the Blocker Structure.

Following the WPZ Conflicts Committee’s meeting, Mr. Chandler participated in a teleconference with Mr. Austin to discuss the WPZ Conflicts Committee’s initial reaction to the potential transaction framework presented by Williams management. Mr. Austin informed Mr. Chandler that the WPZ Conflicts Committee was continuing to evaluate alternative structures to address the financial impacts of the FERC Announcement that the WPZ Conflicts Committee believed may warrant additional analysis to determine if they were more attractive than the transaction framework that had been outlined by Williams management (involving a taxable acquisition by Williams of the WPZ Public Units), including the possibility of the Blocker Structure. Mr. Chandler informed Mr. Austin that members of Williams management had previously evaluated the Blocker Structure and believed that it was financially less attractive to Williams Stockholders and holders of WPZ Common Units than an acquisition of the WPZ Public Units by Williams. Mr. Chandler requested that Mr. Austin provide Williams management with the analysis that the WPZ Conflicts Committee and its advisors had prepared with respect to the Blocker Structure.

On May 2, 2018, members of Williams management participated in a teleconference with representatives of Morgan Stanley, Evercore and Baker Botts, during which the parties discussed the Blocker Structure and the parties’ respective analysis regarding the expected financial impact of that structure as compared to an acquisition of the WPZ Public Units by Williams. During the call, members of Williams management explained the reasons they believed the Blocker Structure was less favorable than such a transaction based on, among other metrics, a net present value analysis. Representatives of Evercore and Baker Botts asked questions regarding Williams management’s analysis regarding the Blocker Structure, and Williams management agreed to share the depreciation schedules for certain subsidiaries of Williams Partners in connection with such analysis.

On May 3, 2018, Mr. Chandler sent to representatives of Evercore additional information regarding tax depreciation and the potential impact on WPZ Public Unitholders of using the Blocker Structure.

On May 4, 2018, representatives of Baker Botts received access to the electronic data room from Williams. Evercore and Baker Botts continued their ongoing financial and legal analyses, respectively, and their due diligence review. Later that day, members of Williams management participated in a teleconference with representatives from Evercore and Baker Botts to further discuss the Blocker Structure and Williams’ management presented its reasoning for why the Blocker Structure was unlikely to address the financial impact of the FERC Announcement in a more attractive manner to the holders of WPZ Public Units than an acquisition of the WPZ Public Units by Williams.

On May 7, 2018, the WPZ Conflicts Committee held a teleconference with representatives of Baker Botts, including its tax and regulatory specialists, and Evercore to receive updates regarding the WPZ Conflicts Committee’s and Evercore’s latest discussions with Williams management and Morgan Stanley, relating to the merger consideration and exploration of the various alternatives discussed during the WPZ Conflicts Committee’s prior meeting on May 1, 2018. The participants discussed the various potential advantages and disadvantages of the alternatives explored, as compared to an exchange ratio of 1.384x, and agreed that the potential alternative transactions were less attractive than the potential merger transaction. After further discussion, the WPZ Conflicts Committee determined that a 1.7026x exchange ratio would be appropriate.

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Subsequently, Mr. Austin participated in a teleconference with Mr. Chandler to present the WPZ Conflicts Committee’s thoughts with respect to Williams management’s illustrative views on the exchange ratio. Mr. Austin stated the view of the WPZ Conflicts Committee that an exchange ratio of 1.7026x would be appropriate.

Later that evening, following discussions with representatives of Morgan Stanley and other members of Williams management, Mr. Chandler informed Mr. Austin that Williams management believed that an exchange ratio of 1.420x would be more appropriate.

On May 8, 2018, the WPZ Conflicts Committee held a teleconference with representatives of Evercore and Baker Botts to update its advisors on the latest development. The participants discussed the spread between Williams management’s and the WPZ Conflicts Committee’s desired exchange ratios. Members of the WPZ Conflicts Committee reiterated that the exchange ratio must be sufficiently compelling and reflect a premium to the Unaffected Spot Exchange Ratio (as defined below). After robust discussions, the WPZ Conflicts Committee determined to present to Williams management that the WPZ Conflicts Committee would be willing to support an exchange ratio of 1.600x.

Subsequently, Mr. Chandler participated in a teleconference with Mr. Austin during which Mr. Austin stated that the WPZ Conflicts Committee would be willing to support an exchange ratio of 1.600x.

Later that day, representatives of Morgan Stanley participated in a teleconference with representatives from Evercore to discuss the WPZ Conflicts Committee’s views on the exchange ratio and Evercore’s analysis in connection therewith.

On May 9, 2018, representatives of Morgan Stanley participated in multiple teleconferences with representatives from Evercore to discuss each advisor’s financial analysis regarding the appropriate exchange ratio should the parties move forward with a transaction involving Williams’ acquisition of the WPZ Public Units.

On May 9, 2018, members of Williams management participated in a teleconference with members of the WPZ Conflicts Committee. Members of Williams management informed the WPZ Conflicts Committee that they could not support an exchange ratio of 1.600x and did not believe the Williams Board would support such an exchange ratio. The WPZ Conflicts Committee acknowledged that following the FERC Announcement, the exchange ratio (based on the trading prices of the Williams Common Stock and the WPZ Common Units) had moved in favor of the WPZ Public Unitholders, and that the WPZ Conflicts Committee believed that any negotiation regarding an exchange ratio in connection with a potential transaction should be based on the exchange ratio of the closing prices on March 15, 2018 (such exchange ratio to be referred to as the “Unaffected Spot Exchange Ratio”). The WPZ Conflicts Committee suggested that they would consider a 15% premium to the Unaffected Spot Exchange Ratio. Members of Williams management suggested that an exchange ratio of 1.450x, representing a 10.3% premium to the Unaffected Spot Exchange Ratio, with an upward adjustment to the exchange ratio in the event that an acquisition by Williams of the WPZ Public Units closed following the record date for the Williams quarterly dividend payable during the third quarter, was in the range that Williams management could support and recommend to the Williams Board if such a transaction was to be pursued.

Later that day, members of Williams management participated in a teleconference with Mr. Austin, in which Williams management previewed a possible exchange ratio equal to 1.494x, which would increase to 1.513x if an acquisition by Williams of the WPZ Public Units closed following the record date for the Williams quarterly dividend payable in the third quarter. Mr. Austin responded that the alternative might be a construct that could be workable for the WPZ Conflicts Committee, contingent upon negotiation and agreement on all deal terms.

Following such discussion, the WPZ Conflicts Committee held another teleconference with representatives of Evercore and Baker Botts to provide updates following Mr. Austin’s discussions with Williams management earlier that afternoon.

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Later that evening, representatives of Gibson Dunn sent an initial draft of a merger agreement to representatives of Baker Botts. Baker Botts distributed the draft to the WPZ Conflicts Committee and representatives of Evercore and RLF for the group’s review and comment. Consistent with the conversation between Williams management and the WPZ Conflicts Committee, the draft merger agreement provided for consideration consisting of an exchange of shares of Williams Common Stock for each WPZ Public Unit. Additionally, the draft merger agreement included many other terms that had not yet been discussed between Williams management and the WPZ Conflicts Committee, including that Williams would be required to pay Williams Partners a termination fee of up to $410 million (payable in four quarterly installments) if the merger agreement was terminated under certain circumstances, which fee amount was consistent with the termination fee that was payable under the 2015 WPZ Merger Agreement. The draft merger agreement had not been discussed with or approved by the Williams Board.

On May 10, 2018, the Williams Board held a regularly-scheduled in-person meeting. At the meeting, members of Williams management updated the Williams Board on discussions with the WPZ Conflicts Committee regarding a potential transaction, and representatives from Morgan Stanley provided financial analysis regarding the exchange ratio that was under discussion. As part of the oversight by the Williams Board, Williams management updated the Williams Board that, with the assistance of Morgan Stanley and Gibson Dunn and subject to the approval of the Williams Board, Williams management would (i) continue to discuss with the WPZ Conflicts Committee and their advisors the terms of a potential transaction, (ii) provide a further update to the Williams Board once more definitive terms were available for the Williams Board to consider and (iii) seek approval by the Williams Board if Williams management and the WPZ Conflicts Committee would be inclined to proceed with the potential transaction as the preferred approach and could come to mutually acceptable terms regarding a potential transaction. The Williams Board took no action at this meeting with respect to a transaction.

Later that day, Mr. Chandler and Mr. Austin participated in a teleconference. During that conversation, Mr. Chandler informed Mr. Austin that Williams management had made minor adjustments to certain components in its financial forecast and that Williams management would be sending an updated financial forecast to the WPZ Conflicts Committee and its advisors reflecting those changes. For further discussion of Williams’ and Williams Partners’ forecasts, see “Unaudited Financial Projections of Williams and Williams Partners.” Mr. Austin informed Mr. Chandler that he had not yet received comments from Baker Botts to the draft merger agreement.

On May 11, 2018, the WPZ Conflicts Committee met to discuss an exchange ratio of 1.494 shares of Williams Common Stock for each WPZ Public Unit or, if the closing does not occur before the record date for Williams’ dividend to be paid in the third quarter of 2018, 1.513 shares of Williams Common Stock in exchange for each WPZ Public Unit. The WPZ Conflicts Committee held a teleconference with representatives of Baker Botts, including its tax specialists, and Evercore to discuss the status of pending negotiations, due diligence efforts and next steps. Representatives of Baker Botts also walked the WPZ Conflicts Committee members through the key provisions of the initial draft merger agreement received on May 9, 2018 from Gibson Dunn and possible revisions to be proposed to Williams which included, among other things, more restrictive interim operating covenants (including certain restrictions on Williams’ ability to issue equity between signing and closing), an express no shop provision restricting the ability of Williams to solicit alternative proposals, the ability for Williams Partners to receive a termination fee in the event Williams terminates the transaction (based on a change of recommendation by the Williams Board) for a superior proposal or in light of an intervening event, or if within twelve months of termination of this transaction Williams enters into or closes a sale of itself to a third party acquirer, reimbursement of Williams Partners’ out-of-pocket expenses if the merger agreement is terminated due to Williams’ uncured breach, an extension of the termination date of the merger agreement from November 30, 2018 to December 31, 2018, provisions for direct indemnification of the members of the WPZ Conflicts Committee by Williams, affirmative obligations for Williams to notify the WPZ Conflicts Committee promptly in writing of any alternative proposals, offers or inquiries received, and other related deal protection provisions. Following this discussion of the merger agreement, the WPZ Conflicts Committee instructed Baker Botts to prepare a revised draft of the merger agreement incorporating the suggested revisions.

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On the afternoon of May 14, 2018, the WPZ Conflicts Committee participated in a teleconference with representatives of Baker Botts and Evercore to discuss updated financial projections that Evercore had received from Williams management over the weekend, the mechanics of the exchange ratios under discussion, subject to adjustment depending on the timing of closing, and the list of desired revisions for Baker Botts to incorporate in a return markup responsive to Gibson Dunn’s draft, including the various recommended deal protections discussed during the WPZ Conflicts Committee’s May 11, 2018 meeting.

Subsequently, representatives from Baker Botts sent a revised draft of the merger agreement to Gibson Dunn containing revisions they had discussed with the WPZ Conflicts Committee. The revised draft, among other things, (i) provided that the merger could not close before the record date for the Williams Partners distribution to be paid in the third quarter of 2018, (ii) included a “no-shop” provision applicable to Williams, (iii) limited the circumstance under which the Williams Board would be permitted to change its recommendation with respect to the Merger, (iv) provided for expense reimbursement of Williams Partners’ transaction expenses (subject to a $10 million cap) payable by Williams under specified circumstances, (v) expanded the scope of interim operating covenants to which Williams would be subject, and (vi) included certain changes to the mechanics for the payment of the termination fee (but made no changes to the termination fee amount).

On May 15, 2018, representatives of Gibson Dunn distributed to Baker Botts a revised draft of the merger agreement. The revised draft, among other things, (i) deleted various proposed interim operating covenants, (ii) modestly narrowed the scope of the no-shop covenant, (iii) added the ability for the Williams Board to change its recommendation with respect to the Merger in connection with an intervening event, and (iv) narrowed the circumstance under which Williams would be required to reimburse Williams Partners’ transaction expenses in connection with a termination of the merger agreement.

Later that evening, the WPZ Conflicts Committee participated in a teleconference with representatives of Baker Botts, including its tax specialists, and Evercore to discuss the current status of the merger agreement draft and determine which outstanding provisions the WPZ Conflicts Committee desired to negotiate further, including, among other points, for the expense reimbursement requirement of up to $10 million in the event the merger agreement is terminated due to Williams’ uncured breach and the WPZ Conflicts Committee’s desire to lower or eliminate altogether the $4 billion threshold for Williams’ ability to issue additional securities. In addition, the participants discussed Williams’ continued reiteration of its desire for flexibility to issue preferred stock, subject to limitations and restrictions proposed by the WPZ Conflicts Committee. The participants also discussed the necessary steps and timeline to closing, assuming the parties reached a mutual agreement on the final exchange ratio, legal documentation and other business terms of the potential transaction and assuming the respective boards approve the transaction.

Later that evening, Baker Botts sent a revised draft of the merger agreement to Gibson Dunn containing the additional revisions discussed with the WPZ Conflicts Committee.

Between the evening of May 15, 2018 and the morning of May 16, 2018, representatives of Gibson Dunn and Baker Botts continued to exchange drafts of the various transaction documents (including, among other things, to reflect Williams’ reduced ability to issue its securities prior to the closing of the transaction from $4 billion to $2 billion), and held multiple conference calls in an effort to finalize, subject to review by the WPZ Conflicts Committee and Williams management and to the review and approval of the Williams Board, the terms of the merger agreement and the schedules and exhibits thereto. On the morning of May 16, 2018, Baker Botts distributed to Gibson Dunn a revised draft of the merger agreement, which was in near final form.

On the morning of May 16, 2018, the WPZ Conflicts Committee held a meeting by teleconference with representatives of Baker Botts, including its tax and regulatory specialists, and Evercore. During this meeting, Baker Botts discussed the updates on the merger agreement since the prior meeting of the WPZ Conflicts Committee.

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Following this discussion, representatives of Evercore reviewed their financial analysis of the Merger Consideration with the WPZ Conflicts Committee. Upon the request of the WPZ Conflicts Committee, Evercore then rendered its oral opinion, which was subsequently confirmed by delivery of a written opinion, that, as of May 16, 2018 and based upon and subject to the assumptions made, procedures followed, matters considered, qualifications and limitations on the scope of review undertaken by Evercore set forth in its opinion, the Merger Consideration to be received by the WPZ Public Unitholders pursuant to the Merger Agreement was fair, from a financial point of view, to the WPZ Public Unitholders. Evercore also reiterated to the WPZ Conflicts Committee the nature of its relationship to and engagement for Williams, Williams Partners and their affiliates during the past two years and the amount and nature of the fees it received from such parties. The WPZ Conflicts Committee then adjourned for a recess until reconvening that afternoon.

Following the morning’s teleconference with the WPZ Conflicts Committee, representatives of Gibson Dunn and Baker Botts held a conference call to negotiate and finalize the terms of the merger agreement and related documentation. Later that morning, Gibson Dunn sent a further revised draft of the merger agreement to Baker Botts reflecting the final agreed upon terms, subject to formal approval by the WPZ Conflicts Committee at its meeting later that day.

That afternoon, the WPZ Conflicts Committee reconvened its meeting via teleconference with representatives from Baker Botts, including its tax and regulatory specialists, and Evercore. Baker Botts reviewed the efforts made by the WPZ Conflicts Committee since it commenced work, including the substantive work and processes followed, noting that the WPZ Conflicts Committee had met frequently. Baker Botts then summarized its legal due diligence review in connection with the potential transaction, which covered corporate, tax, real estate, regulatory, environmental, employment benefits and litigation matters. The WPZ Conflicts Committee discussed its duties with respect to the potential transaction and reviewed the “Special Approval” standard under the partnership agreement of Williams Partners.

Following such presentation, the WPZ Conflicts Committee discussed and then unanimously (i) determined that the Merger Agreement and the transactions contemplated thereby are in the best interest of Williams Partners and the WPZ Public Unitholders, (ii) approved the Merger Agreement and the transactions contemplated thereby, including the Merger (the foregoing constituting Special Approval under the partnership agreement of Williams Partners), and (iii) approved, and recommended to the WPZ Board the approval of, the Merger Agreement and the consummation of the transactions contemplated thereby, including the Merger. See “Reasons for the WPZ Conflicts Committee’s Recommendation.”

On the afternoon of May 16, 2018, the WPZ Board held a telephonic meeting. After discussion, upon receipt of the recommendation of the WPZ Conflicts Committee, the WPZ Board unanimously (i) approved the Merger Agreement and the transactions contemplated thereby, including the Merger, and (ii) directed that the Merger Agreement be submitted to a vote of the holders of WPZ Units by written consent pursuant to the terms of the Williams Partners partnership agreement.

On the evening of May 16, 2018, the Williams Board held a special board meeting attended by eight of the ten directors, as well as members of Williams management and representatives of Morgan Stanley. Members of Williams management reviewed with the Williams Board the legal and financial terms of the proposed Merger, including the principal benefits of the proposed Merger. For a discussion of such principal benefits of the Merger, see “Recommendation of the Williams Board and Its Reasons for the Merger.” Representatives of Morgan Stanley provided the Williams Board with updated financial and market perspectives regarding Williams and the potential pro forma financial impact of the proposed Merger on Williams. The representatives of Morgan Stanley then presented its financial analyses regarding the consideration payable in the Merger and delivered its oral opinion to the Williams Board, which was confirmed by delivery of a written opinion dated May 16, 2018, that, as of such date and based upon and subject to the various assumptions made, procedures followed, matters considered and qualifications and limitations on the scope of review undertaken by Morgan Stanley as set forth therein, the Merger Consideration to be paid by Williams pursuant to the Merger Agreement was fair, from a financial point of view, to Williams. Following review and discussions among the members of the Williams

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Board, the members of the Williams Board in attendance unanimously determined that the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Merger, are in the best interests of the Williams Stockholders, and the members of the Williams Board in attendance unanimously voted to approve the Merger Agreement and the transactions contemplated thereby and recommend that the Williams Stockholders approve the Stock Issuance Proposal and Charter Amendment Proposal.

Thereafter, on May 16, 2018, the parties executed the definitive transaction documents.

Early in the morning on May 17, 2018, Williams and Williams Partners issued a press release announcing the transactions.

Resolution of Conflicts of Interest; Standards of Conduct and Modification of Duties

The approval of the Merger Agreement and the transactions contemplated thereby, including the Merger, by a majority of the members of the WPZ Conflicts Committee constitutes “Special Approval” under the Williams Partners partnership agreement. Under Section 7.9(a) of the Williams Partners partnership agreement, whenever a potential conflict of interest exists, such as consideration of the Merger Agreement and the transactions contemplated thereby, including the Merger, any resolution or course of action by the WPZ General Partner or its affiliates in respect of such conflict of interest will be permitted and deemed approved by all of the partners of Williams Partners and will not constitute a breach of the Williams Partners partnership agreement or of any duty stated or implied by law, in equity or otherwise, if the resolution or course of action is approved by Special Approval, namely approval by a majority of the members of the WPZ Conflicts Committee.

Under Section 7.10(b) of the Williams Partners partnership agreement, any action taken or omitted to be taken by the WPZ General Partner in reliance upon the advice or opinion of an investment banker, among others, as to matters reasonably believed to be in such person’s professional or expert competence shall be “conclusively presumed to have been done or omitted in good faith and in accordance with such opinion.”

Recommendation of the WPZ Conflicts Committee and the WPZ Board

The WPZ Conflicts Committee consists of three independent directors: H. Brent Austin (Chairman), Philip L. Frederickson and Alice M. Peterson. The WPZ Board authorized the WPZ Conflicts Committee to (i) review and evaluate the terms and conditions, and determine the advisability, of a potential transaction involving the acquisition of the WPZ Public Units by Williams, (ii) make such investigation of potential alternatives to such transaction, including maintaining the status quo, as the WPZ Conflicts Committee deems necessary or appropriate, (iii) negotiate, or delegate the ability to negotiate to any persons, with any party the WPZ Conflicts Committee deems appropriate, with respect to the terms and conditions of such transaction, (iv) determine whether to give or withhold the WPZ Conflicts Committee’s approval of such transaction, including by Special Approval pursuant to Section 7.9(a) of the Williams Partners partnership agreement, and (v) make a recommendation to the WPZ Board whether to approve such transaction.

The WPZ Conflicts Committee retained Baker Botts as its legal counsel, RLF as its Delaware legal counsel and Evercore as its independent financial advisor. The WPZ Conflicts Committee believed that Evercore was independent based on the lack of material business relationships between Evercore and Williams, Williams Partners or their affiliates (other than prior representations of the WPZ Conflicts Committee). The WPZ Conflicts Committee oversaw the performance of financial and legal due diligence by its advisors, conducted an extensive review and evaluation of the potential transaction, including with respect to withholding Special Approval and maintaining the status quo, and conducted extensive negotiations with Williams and its representatives with respect to the Merger Agreement and other related agreements.

The WPZ Conflicts Committee, by unanimous vote at a meeting held on May 16, 2018, (i) determined that the Merger Agreement and the transactions contemplated thereby are in the best interests of Williams Partners and the WPZ Public Unitholders, (ii) approved the Merger Agreement and the transactions contemplated thereby,

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including the Merger (such approval constituting Special Approval), and (iii) approved, and recommended to the WPZ Board the approval of, the Merger Agreement and the consummation of the transactions contemplated thereby, including the Merger.

Upon receipt of such recommendation, the WPZ Board, by unanimous vote at a meeting held on May 16, 2018, (i) deemed it advisable and in the best interests of Williams Partners, the WPZ General Partner and the WPZ Public Unitholders that the Partnership enter into the Merger Agreement and consummate the Merger, (ii) approved the Merger and the other transactions contemplated by the Merger Agreement, (iii) approved the form, terms and provisions of the Merger Agreement and the Support Agreement, the consummation of the transactions contemplated thereby and the execution, delivery and performance by the WPZ General Partner and Williams Partners of the Merger Agreement and the Support Agreement, (iv) directed that the Merger Agreement be submitted to a vote of the Limited Partners (as defined in the Williams Partners partnership agreement) and (vi) authorized the Limited Partners to act by written consent without a meeting in connection with consenting to the Merger Agreement and the transactions contemplated thereby, including, without limitation, the Merger.

Reasons for the WPZ Conflicts Committee’s Recommendation

The WPZ Conflicts Committee consists of three independent directors: H. Brent Austin (Chairman), Philip L. Frederickson and Alice M. Peterson. The WPZ Board authorized the WPZ Conflicts Committee to (i) review and evaluate the terms and conditions, and determine the advisability of a potential transaction involving the acquisition of the WPZ Public Units by Williams, (ii) make such investigation of potential alternatives to such transaction, including maintaining the status quo, as the WPZ Conflicts Committee deemed necessary or appropriate, (iii) with respect to the terms and conditions of such transaction, negotiate, or delegate the ability to negotiate to any persons, with any party the WPZ Conflicts Committee deemed appropriate, (iv) determine whether to give or withhold the WPZ Conflicts Committee’s approval of such transaction, including by “Special Approval” pursuant to Section 7.9(a) of the Williams Partners limited partnership agreement, and (v) make a recommendation to the WPZ Board whether to approve such transaction.

The WPZ Conflicts Committee retained Baker Botts as its legal counsel, RLF as its Delaware legal counsel and Evercore as its independent financial advisor. The WPZ Conflicts Committee believed that Evercore was independent based on the lack of business relationships between Evercore and Williams, Williams Partners or their affiliates (other than prior representations of the WPZ Conflicts Committee). The WPZ Conflicts Committee oversaw the performance of financial and legal due diligence by its advisors, conducted an extensive review and evaluation of the potential transaction with Williams, including with respect to evaluating alternative transactions or withholding Special Approval and maintaining the status quo, and conducted extensive negotiations with Williams and its representatives with respect to the Merger Agreement and other related agreements.

The WPZ Conflicts Committee, by unanimous vote at a meeting held on May 16, 2018, (i) determined that the Merger Agreement and the transactions contemplated thereby are in the best interests of Williams Partners and the WPZ Public Unitholders, (ii) approved the Merger Agreement and the transactions contemplated thereby, including the Merger (such approval constituting Special Approval), and (iii) approved, and recommended to the WPZ Board the approval of, the Merger Agreement and the consummation of the transactions contemplated thereby, including the Merger.

Upon receipt of such recommendation, the WPZ Board, by unanimous vote at a meeting held later that afternoon, (i) deemed it advisable and in the best interests of Williams Partners and the WPZ Public Unitholders that the Partnership enter into the Merger Agreement and consummate the Merger, (ii) deemed it advisable and in the best interests of the WPZ General Partner that the WPZ General Partner enter into the Merger Agreement and consummate the Merger and engage in all transactions related thereto, (iii) approved and authorized the Merger and the other transactions contemplated by the Merger Agreement, (iv) approved the form, terms and provisions of the Merger Agreement and the Support Agreement, the consummation of the transactions contemplated thereby and the execution, delivery and performance by the WPZ General Partner and Williams Partners of the

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Merger Agreement and the Support Agreement, (v) directed that the Merger Agreement be submitted to a vote of the Limited Partners (as defined in the Williams Partners limited partnership agreement) and (vi) authorized the Limited Partners to act by written consent without a meeting in connection with consenting to the Merger Agreement and the transactions contemplated thereby, including, without limitation, the Merger.

Many of the factors considered by the WPZ Conflicts Committee favored its determination that the Merger Agreement and the transactions contemplated thereby are in the best interests of Williams Partners and the WPZ Public Unitholders, including the following:

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The WPZ Conflicts Committee considered the following factors to be generally negative or unfavorable in making its determination that the Merger Agreement and the transactions contemplated thereby are in the best interests of Williams Partners and the WPZ Public Unitholders:

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In addition to the factors described above, the WPZ Conflicts Committee considered the following procedural factors in making its determination that the Merger Agreement and the transactions contemplated thereby are in the best interests of Williams Partners and the WPZ Public Unitholders:

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After taking into account all of the factors set forth above, as well as others, the WPZ Conflicts Committee concluded that the potential benefits of the Merger outweighed any negative or unfavorable considerations and determined that the Merger Agreement and the transactions contemplated thereby are in the best interests of Williams Partners and the WPZ Public Unitholders.

The foregoing discussion is not intended to be exhaustive but is intended to address the material information and principal factors considered by the WPZ Conflicts Committee in considering the Merger. In view of the number and variety of factors and the amount of information considered, the WPZ Conflicts Committee did not find it practicable to, and did not make specific assessments of, quantify or otherwise assign relative weights to, the specific factors considered in reaching its determination. In addition, the WPZ Conflicts Committee did not undertake to make any specific determination as to whether any particular factor, or any aspect of any particular factor, was favorable or unfavorable to its ultimate determination, and individual members of the WPZ Conflicts Committee may have given different weights to different factors. The WPZ Conflicts Committee made its recommendation based on the totality of information presented to, and the investigation conducted by, the WPZ Conflicts Committee. It should be noted that certain statements and other information presented in this section are forward-looking in nature and, therefore, should be read in light of the factors discussed under the heading “Information Regarding Forward-Looking Statements.”

Unaudited Financial Projections of Williams and Williams Partners

In connection with the proposed Merger, management of Williams provided projections relating to Williams and Williams Partners that included future financial and operating performance. The projections were prepared for Williams and Williams Partners on a stand-alone basis, and reflected the anticipated impact of the FERC Announcement during the periods presented. These non-public projections were provided to Evercore for use and consideration in its financial analysis and in preparation of its opinion to the WPZ Conflicts Committee and to Morgan Stanley for use and consideration in its financial analysis and in preparation of its opinion to the Williams Board. A summary of these projections is included below to give holders of WPZ Public Units and Williams Common Stock access to certain non-public unaudited prospective financial information that was made available to Evercore, Morgan Stanley, the WPZ Conflicts Committee, the WPZ Board, and the Williams Board in connection with the proposed Merger.

You should be aware that uncertainties are inherent in prospective financial information of any kind. None of Williams or Williams Partners or any of their affiliates, advisors, officers, directors, or representatives has made or makes any representation or can give any assurance to any WPZ Unitholder or Williams Stockholder, or any other person regarding the ultimate performance of Williams Partners or Williams compared to the summarized information set forth below or that any such results will be achieved.

The summary projections set forth below summarize the projections made available to the legal and financial advisors to each of the parties to the transaction. The inclusion of the following summary projections in

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this joint consent statement/proxy statement/prospectus should not be regarded as an indication that Williams Partners, Williams, or their respective representatives considered or consider the projections to be a reliable or accurate prediction of future performance or events, and the summary projections set forth below should not be relied upon as such.

The Williams and Williams Partners projections summarized below were prepared by employees of Williams. The Williams and Williams Partners projections were only prepared for internal planning purposes and not with a view toward public disclosure or toward compliance with GAAP, the published guidelines of the SEC, or the guidelines established by the American Institute of Certified Public Accountants. None of Ernst & Young LLP (“Ernst & Young”), PricewaterhouseCoopers LLP (“PwC”), or Deloitte & Touche LLP (“DT”), nor any other independent registered public accounting firm has audited, reviewed, compiled, examined or performed any procedures with respect to the prospective financial information contained in the projections, and accordingly, none of Ernst & Young, PwC, or DT expresses an opinion or any other form of assurance with respect thereto. The Ernst & Young reports incorporated by reference into this joint consent statement/proxy statement/prospectus with respect to Williams Partners relate to historical financial information of Williams Partners and the PwC and DT reports incorporated by reference into this joint consent statement/proxy statement/prospectus with respect to Gulfstream relate to historical financial information of Gulfstream. Such reports do not extend to the projections included below and should not be read to do so. Neither the WPZ Board nor the Williams Board prepared, and none of the WPZ Board, the WPZ Conflicts Committee, the WPZ General Partner, Williams Partners, or the Williams Board gives any assurance regarding, the summarized information.

The internal financial projections of Williams and Williams Partners are, in general, prepared primarily for internal use. Such internal financial forecasts are inherently subjective in nature, susceptible to interpretation and, accordingly, such forecasts may not be achieved. The internal financial forecasts also reflect numerous assumptions made by management, including material assumptions that may not be realized and are subject to significant uncertainties and contingencies, all of which are difficult to predict and many of which are beyond the control of the preparing party. Williams management, consistent with past presentations to the WPZ Board and public guidance representations, develops its financial forecasts according to several criteria, including commodity price sensitivities. Additionally, prospective mergers and acquisitions and any prospective projects were excluded from the financial projections. Accordingly, there can be no assurance that the assumptions made in preparing the internal financial forecasts upon which the foregoing projected financial information was based will prove accurate. There will be differences between actual and forecasted results, and the differences may be material. The risk that these uncertainties and contingencies could cause the assumptions to fail to be reflective of actual results is further increased due to the length of time in the future over which these assumptions apply. Any inaccuracy of assumptions and projections in early periods could have a compounding effect on the projections shown for the later periods. Thus, any failure of an assumption or projection to be reflective of actual results in an early period could have a greater effect on the projected results failing to be reflective of actual events in later periods.

All of these assumptions involve variables making them difficult to predict, and some are beyond the control of Williams Partners and Williams. Although Williams’ management believes that there was a reasonable basis for its projections and underlying assumptions, any assumptions for near-term projected cases remain uncertain, and the risk of inaccuracy increases with the length of the forecasted period. The projections are forward-looking statements and are subject to risks and uncertainties. See “Information Regarding Forward-Looking Statements.”

In developing the projections, Williams’ management made numerous material assumptions with respect to Williams and Williams Partners for the period from 2018 to 2020, including:

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The summarized projected financial information set forth below was based on Williams’ and Williams Partners’ stand-alone projected results for 2018 through 2020, and, therefore include the estimated impact of the FERC Announcement.

NEITHER WILLIAMS PARTNERS NOR WILLIAMS INTEND TO UPDATE OR OTHERWISE REVISE THE ABOVE PROSPECTIVE FINANCIAL INFORMATION TO REFLECT CIRCUMSTANCES EXISTING AFTER THE DATE SUCH PROSPECTIVE FINANCIAL INFORMATION WAS PREPARED OR TO REFLECT THE OCCURRENCE OF SUBSEQUENT EVENTS, EVEN IN THE EVENT THAT ANY OR ALL OF THE ASSUMPTIONS UNDERLYING SUCH PROSPECTIVE FINANCIAL INFORMATION ARE NO LONGER APPROPRIATE.

Opinion of Evercore — Financial Advisor to the WPZ Conflicts Committee

The WPZ Conflicts Committee retained Evercore to act as its financial advisor in connection with evaluating the proposed Merger. At the request of the WPZ Conflicts Committee at a meeting of the WPZ Conflicts Committee held on May 16, 2018, Evercore rendered its oral opinion to the WPZ Conflicts Committee (subsequently confirmed in writing) that, as of May 16, 2018, based upon and subject to the assumptions made, procedures followed, matters considered, qualifications and limitations on the scope of review undertaken by Evercore in connection with the preparation of its opinion as set forth therein, the Merger Consideration to be received by the WPZ Public Unitholders pursuant to the Merger Agreement was fair, from a financial point of view, to the WPZ Public Unitholders.

The opinion speaks only as of the date it was delivered and not as of the time the Merger will be completed or any other date. The opinion does not reflect changes that may occur or may have occurred after May 16, 2018, which could alter the facts and circumstances on which Evercore’s opinion was based. It is understood that subsequent events may affect Evercore’s opinion, but Evercore does not have any obligation to update, revise or reaffirm its opinion.

The full text of the written opinion of Evercore, which sets forth the assumptions made, procedures followed, matters considered, qualifications and limitations of the review undertaken in rendering its opinion, is attached hereto as Annex B. You are urged to read Evercore’s opinion carefully and in its entirety. Evercore’s opinion was directed to the WPZ Conflicts Committee (in its capacity as such), and only addressed the fairness, from a financial point of view, as of May 16, 2018, to the WPZ Public Unitholders of the Merger Consideration to be received by the WPZ Public Unitholders pursuant to the Merger Agreement. Evercore’s opinion did not address any other term, aspect or implications of the Merger. Neither Evercore’s opinion, the summary of such opinion nor the related analyses set forth in this joint consent statement/proxy statement/prospectus are intended to be, and they do not constitute, a recommendation to the WPZ Conflicts Committee or to any other person in respect of the Merger or any other matter, including as to how any holder of WPZ Common Units should act or vote in respect of the Merger. The summary of Evercore’s opinion set forth in this joint consent statement/proxy statement/prospectus is qualified in its entirety by reference to the full text of the written opinion.

In connection with rendering its opinion and performing its related financial analyses, Evercore, among other things:

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For purposes of its analysis and opinion, Evercore assumed and relied upon, without undertaking any independent verification of, the accuracy and completeness of all of the information publicly available and all of the information supplied or otherwise made available to, discussed with, or reviewed by Evercore and upon the assurances of the management of Williams Partners that they were not aware of any relevant information that has been omitted or that remains undisclosed to Evercore, and Evercore assumed no liability therefor. With respect to the projected financial and operating data relating to Williams Partners and Williams, Evercore assumed that they had been reasonably prepared on bases reflecting the best currently available estimates and good faith judgments of the respective managements of Williams Partners and Williams as to the future financial performance of Williams Partners and Williams, as applicable, under the assumptions stated therein. Evercore expressed no view as to the projected financial and operating data or any judgments, estimates or assumptions on which they were based. Evercore relied at the WPZ Conflicts Committee’s direction, without independent verification, upon the assessments of the management of each of Williams Partners and Williams as to the future financial and operating performance of Williams Partners and Williams.

For purposes of rendering its opinion, Evercore assumed, in all respects material to its analysis, that the Merger Agreement, the Support Agreement and any other related agreement (collectively, the “Transaction Agreements”) would be executed and delivered in the draft forms reviewed by Evercore, that the representations and warranties of each party contained in the Transaction Agreements (in the draft forms reviewed by Evercore) were true and correct in all material respects, that each party would perform all of the covenants and agreements required to be performed by it under the Transaction Agreements and applicable law and the governing documents of each of Williams Partners and Williams, including, but not limited to, the cancellation and retirement of WPZ Common Units owned by Williams Partners (collectively, the “Merger Related Actions”), and that all conditions to the consummation of the Merger, including the Merger Related Actions and transactions related to the Transaction Agreements, would be satisfied without material waiver or modification thereof. Evercore further assumed, with the WPZ Conflicts Committee’s consent, that the Merger and transactions related to the Transaction Agreements would be consummated in accordance with their terms, without waiver, modification or further amendment of any material term, condition or agreement and that all governmental, regulatory or other consents, approvals or releases necessary for the consummation of the Merger and transactions related to the Transaction Agreements would be obtained without any material delay, limitation, restriction or condition that would have an adverse effect on Williams Partners, Williams, the consummation of the Merger or any transactions related to the Transaction Agreements, or materially reduce the benefits of the Merger to Williams Partners. Evercore assumed the final versions of all documents reviewed by it in draft form will conform in all material respects to the drafts reviewed by it.

Evercore did not make nor did it assume any responsibility for making any independent valuation or appraisal of the assets or liabilities of Williams Partners or Williams, nor was Evercore furnished with any such appraisals, nor did it evaluate the solvency or fair value of Williams Partners or Williams under any state or federal laws relating to bankruptcy, insolvency or similar matters. Evercore’s opinion is necessarily based upon information made available to it as of the date of its opinion and financial, economic, monetary, market, regulatory and other conditions and circumstances as they existed and as could be evaluated on the date thereof.

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Evercore was not asked to pass upon, and expressed no opinion with respect to, any matter other than the fairness, from a financial point of view, to the WPZ Public Unitholders of the Merger Consideration to be received by the WPZ Public Unitholders pursuant to the Merger Agreement. Evercore did not express any view on, and its opinion did not address, the fairness of the Merger to any other persons or the holders of any other securities, creditors or other constituencies of Williams Partners, nor any view as to the fairness of the amount or nature of any compensation to be paid or payable to any of the officers, directors or employees of Williams Partners or any of the other parties to the Merger Agreement or any affiliates thereof, or any classes of such persons, whether relative to the Merger Consideration or otherwise. In addition, Evercore’s opinion did not address any tax consequences of the Merger to any WPZ Public Unitholder. Evercore assumed that any modification to the structure of the Merger would not vary in any respect material to its analysis. Evercore’s opinion did not address the relative merits of the Merger as compared to other business or financial strategies that might be available to Williams Partners or Williams, nor did it address the underlying business decision of Williams Partners to engage in the Merger. Evercore’s opinion did not constitute a recommendation to the WPZ Conflicts Committee or to any other persons in respect of the Merger. Evercore expressed no opinion as to the price at which the WPZ Common Units or Williams Common Stock will trade at any time. The opinion noted that Evercore is not a legal, regulatory, accounting or tax expert and that Evercore assumed the accuracy and completeness of assessments by the management of Williams Partners and their advisors with respect to legal, regulatory, accounting and tax matters.

Set forth below is a summary of the material financial analyses performed by Evercore and reviewed with the WPZ Conflicts Committee on May 16, 2018, in connection with rendering its opinion to the WPZ Conflicts Committee. Each analysis was provided to the WPZ Conflicts Committee. The following summary, however, does not purport to be a complete description of the analyses performed by Evercore. In connection with arriving at its opinion, Evercore considered all of its analyses as a whole, and the order of the analyses described and the results of these analyses do not represent any relative importance or particular weight given to these analyses by Evercore. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data (including the closing prices for WPZ Common Units and shares of Williams Common Stock) that existed on May 16, 2018, and is not necessarily indicative of current market conditions.

The following summary of financial analyses includes information presented in tabular format. These tables must be read together with the text of each summary in order to fully understand the financial analyses performed by Evercore. The tables alone do not constitute a complete description of the financial analyses performed by Evercore. Considering the tables below without considering the full narrative description of the financial analyses, including the methodologies and assumptions underlying the analyses, could create a misleading or incomplete view of Evercore’s financial analyses.

Valuation of Williams Partners

Discounted Distribution Analysis

Evercore performed a discounted distribution analysis for Williams Partners based on the projections provided by Williams Partners’ management. Evercore based this analysis on (a) the sum of the present value of Williams Partners’ projected distributions per WPZ Common Unit on a stand-alone basis from the second half of 2018 through year-end 2020 and (b) the present value of the terminal value determined as the quotient of Williams Partners’ projected 2020 distributions per WPZ Common Unit and the projected yield on WPZ Common Units in 2020.

For this analysis, Evercore assumed a range of terminal yields from 6.0% to 8.0% based upon the distribution yield range at which WPZ Common Units traded during the 52-week period prior to May 16, 2018. Evercore also assumed cost of equity discount rates for Williams Partners of 8.0% to 9.0% (based on a capital asset pricing model (“CAPM”)) and 12.5% to 13.5% (based on total expected market return).

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After giving effect to such discounting, this analysis resulted in a range of implied values per WPZ Common Unit of $34.71 to $45.21 based on CAPM, and $31.66 to $41.11 based on total expected market return.

Evercore derived its ranges of discount rates and terminal yields based on, among other things, its professional judgment and experience, including its understanding of the size, relative profitability and expected growth of Williams Partners and the selected peer partnerships to which Evercore compared Williams Partners in the Williams Partners Peer Group Trading Analysis and the multiples and discount rates of those peer partnerships. Evercore’s calculations reflect its review of the full range of discount rates and terminal yields implied by the comparable peer partnerships rather than the application of a mathematical mean or median.

Peer Group Trading Analysis

Evercore performed a peer group trading analysis of Williams Partners by reviewing and comparing the market values and trading multiples of the following 14 publicly traded partnerships that Evercore deemed to have certain characteristics that are similar to Williams Partners, such as market value, asset base and other characteristics:

Large-Cap Diversified MLPs

FERC-Regulated Natural Gas Pipeline MLPs

Gathering & Processing MLPs Greater Than $2.0 Billion Equity Market Value

Although the peer group was compared to Williams Partners for purposes of this analysis, no partnership used in the peer group analysis is identical or directly comparable to Williams Partners. In order to calculate peer group trading multiples, Evercore relied on publicly available filings with the SEC and equity research analyst estimates.

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For each of the peer group partnerships, Evercore calculated the following trading multiples for the Large-Cap Diversified MLPs, FERC-Regulated Natural Gas Pipeline MLPs and Gathering & Processing MLPs Greater Than $2.0 Billion Equity Market Value:

The mean and median trading multiples of the three peer trading groups are set forth below. The table also includes relevant multiple ranges selected by Evercore based on the resulting range of multiples and certain other considerations related to the specific characteristics of the Partnership noted by Evercore.

Based on its review of the peer groups and Evercore’s professional judgment, Evercore selected enterprise value multiple ranges of 9.0x – 11.0x to 2018E EBITDA and 8.25x to 10.25x to 2019E EBITDA.

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Evercore applied the relevant multiples to Williams Partners’ projected 2018E and 2019E Adjusted EBITDA from the projections of Williams Partners’ management (see “The Merger—Unaudited Financial Projections of Williams and Williams Partners”) to determine a selected enterprise value range of $40,686 million to $49,727 million for year-end 2018, and $40,577 million to $50,414 million for year-end 2019. After adjusting for net debt and minority interest as of March 31, 2018 and WPZ Common Units outstanding as of April 30, 2018, Evercore determined an implied equity value per WPZ Common Unit range of $23.35 per WPZ Common Unit to $32.61 per WPZ Common Unit for year-end 2018 and $23.24 per WPZ Common Unit to $33.32 per WPZ Common Unit for year-end 2019.

Precedent M&A Transactions Analysis

Evercore reviewed selected publicly available information for FERC-regulated natural gas pipeline transactions announced between August 2012 and February 2018 and selected 21 transactions involving assets that Evercore deemed to have certain characteristics that are similar to those of Williams Partners’ FERC-regulated natural gas pipelines, although Evercore noted that none of the selected transactions or the selected entities that participated in the selected transactions were directly comparable to the Merger or Williams Partners. Evercore also reviewed selected publicly available information for natural gas gathering and processing transactions announced between February 2016 and April 2018 and selected 26 transactions involving assets that Evercore deemed to have certain characteristics that are similar to those of Williams Partners’ natural gas gathering and processing assets, although Evercore noted that none of the selected transactions or the selected entities that participated in the selected transactions were directly comparable to the Merger or Williams Partners.

Based on a review of the full range of historical enterprise value to EBITDA multiples paid in the selected precedent transactions and its professional judgment, rather than the application of a mathematical mean or median, Evercore applied relevant EBITDA multiples ranging from 9.0x to 11.0x to determine a selected enterprise value range for Williams Partners’ Northeast G&P business segment of $9,945 million to $12,155 million for year-end 2018. Evercore also applied relevant EBITDA multiples ranging from 9.0x to 11.0x to determine a selected enterprise value range for Williams Partners’ Atlantic Gulf business segment of $17,280 million to $21,120 million for year-end 2018. Evercore also applied relevant EBITDA multiples ranging from 8.0x to 10.0x to determine a selected enterprise value range for Williams Partners’ West business segment of $12,504 million to $15,630 million for year-end 2018.

Evercore then conducted a sum-of-the-parts analysis and combined the individual enterprise value ranges for the Northeast G&P, Atlantic Gulf and West business segments to determine a selected enterprise value range for Williams Partners of $39,729 million to $48,905 million for year-end 2018. After adjusting for net debt and minority interest as of March 31, 2018 and WPZ Common Units outstanding as of April 30, 2018, Evercore determined an implied equity value per WPZ Common Unit range of $23.37 per WPZ Common Unit to $31.77 per WPZ Common Unit.

Valuation of Williams

Discounted Dividend Analysis

Evercore performed a discounted dividend analysis for Williams based on the projections provided by Williams’ management. Evercore based this analysis on (a) the sum of the present value of Williams’ projected dividends per share of Williams Common Stock on a stand-alone basis from the second half of 2018 through year-end 2020 and (b) the present value of the terminal value determined as the quotient of Williams’ projected 2020 dividends per share of Williams Common Stock and the projected yield on Williams Common Stock in 2020.

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For this analysis, Evercore assumed a range of terminal yields from 4.0% to 6.0% based upon the dividend yield range at which Williams Common Stock traded during the 52-week period prior to May 16, 2018. Evercore also assumed cost of equity discount rates for Williams of 9.0% to 11.0% (based on CAPM) and 12.5% to 13.5% (based on total expected market return).

After giving effect to such discounting, this analysis resulted in a range of implied values per share of Williams Common Stock of $23.87 to $35.65 based on CAPM, and $22.66 to $33.06 based on total expected market return.

Evercore derived its ranges of discount rates and terminal yields based on, among other things, its professional judgment and experience, including its understanding of the size, relative profitability and expected growth of Williams and the selected peer companies and partnerships to which Evercore compared Williams in the Williams Peer Group Trading Analysis and the multiples and discount rates of those peer companies and partnerships. Evercore’s calculations reflect its review of the full range of discount rates and terminal yields implied by the comparable peer companies and partnerships rather than the application of a mathematical mean or median.

Peer Group Trading Analysis

Evercore performed a peer group trading analysis of Williams based on the peer group trading analysis-implied price per WPZ Common Unit for Williams Partners at year-end 2018 and year-end 2019 to determine an implied enterprise value range for Williams of $16,827 million to $23,503 million for year-end 2018 and $16,746 million to $24,010 million for year-end 2019. After adjusting for net debt as of March 31, 2018 and Williams Common Stock outstanding as of April 30, 2018, Evercore determined an implied equity value range per share of Williams Common Stock of $15.08 to $23.15 for year-end 2018, and $14.99 to $23.76 for year-end 2019.

Precedent M&A Transaction Analysis

Evercore performed a precedent transactions analysis of Williams based on the precedent transactions analysis-implied price per WPZ Common Unit for Williams Partners to determine an implied enterprise value range for Williams of $16,120 million to $22,896 million. After adjusting for net debt as of March 31, 2019 and shares of Williams Common Stock outstanding as of April 30, 2018, Evercore determined an implied equity value range per share of Williams Common Stock of $14.23 to $22.42.

Exchange Ratio Summary

Evercore analyzed the implied exchange ratios from the valuation techniques utilized for the valuation of Williams Partners and Williams. These valuation techniques included discounted distribution/dividend analysis based on CAPM and expected market return, peer group trading analysis and precedent M&A transaction analysis. The low to high exchange ratio using the discounted distribution/dividend analysis based on CAPM was 1.27x to 1.45x. The low to high exchange ratio using a discounted distribution/dividend analysis based on expected market return was 1.24x to 1.40x. The low to high exchange ratio using a peer group trading analysis was 1.41x to 1.55x for year-end 2018 and 1.40x to 1.55x for year-end 2019. The low to high exchange ratio using a precedent M&A transactions analysis was 1.42x to 1.57x.

Evercore compared the results of the foregoing analyses to the proposed exchange ratio of 1.494 shares of Williams Common Stock for each outstanding WPZ Public Unit and the potential exchange ratio of 1.513 shares of WMB Common Stock for each outstanding WPZ Public Unit if the Merger closes on or after the record date for the regular quarterly cash dividend on the Williams Common Stock that is paid or payable during the calendar quarter ending September 30, 2018. The Merger Consideration was within or above the range of the implied exchange ratios for each of the valuation techniques reviewed by Evercore.

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General

The foregoing summary of certain material financial analyses does not purport to be a complete description of the analyses or data presented by Evercore. The WPZ Conflicts Committee selected Evercore to provide financial advice in connection with its evaluation of the proposed Merger because of, among other reasons, Evercore’s experience, reputation and familiarity with the midstream sector of the energy industry and because its investment banking professionals have substantial experience in transactions similar to the Merger. In connection with the review of the Merger, Evercore performed a variety of financial and comparative analyses for purposes of rendering its opinion to the WPZ Conflicts Committee. The preparation of a fairness opinion is a complex process and is not necessarily susceptible to partial analysis or summary description. Selecting portions of the analyses or of the summary described above, without considering the analyses as a whole, could create an incomplete view of the processes underlying Evercore’s opinion. In arriving at its fairness determination, Evercore considered the results of all the analyses and did not draw, in isolation, conclusions from or with regard to any one analysis or factor considered by it for purposes of its opinion. Rather, Evercore made its determination as to fairness on the basis of its experience and professional judgment after considering the results of all the analyses. In addition, Evercore may have given various analyses and factors more or less weight than other analyses and factors, and may have deemed various assumptions more or less probable than other assumptions. As a result, the ranges of valuations resulting from any particular analysis or combination of analyses described above should not be taken to be the view of Evercore with respect to the actual value of WPZ Common Units or the Williams Common Stock. No company or partnership used in the above analyses as a comparison is directly comparable to Williams Partners or Williams, and no precedent transaction used is directly comparable to the Merger. Furthermore, Evercore’s analyses involve complex considerations and judgments concerning financial and operating characteristics and other factors that could affect the acquisition, public trading or other values of the companies, partnerships or transactions used, including judgments and assumptions with regard to industry performance, general business, economic, market and financial conditions and other matters, many of which are beyond the control of Williams Partners or Williams and their respective advisors.

Evercore prepared these analyses solely for the information and benefit of the WPZ Conflicts Committee and for the purpose of providing an opinion to the WPZ Conflicts Committee as to the fairness of the Merger Consideration, from a financial point of view, to the WPZ Public Unitholders. These analyses do not purport to be appraisals or to necessarily reflect the prices at which the business or securities actually may be sold. Any estimates contained in these analyses are not necessarily indicative of actual future results, which may be significantly more or less favorable than those suggested by such estimates. Accordingly, estimates used in, and the results derived from, Evercore’s analyses are inherently subject to substantial uncertainty, and Evercore assumes no responsibility if future results are materially different from those forecasted in such estimates. The issuance of the opinion was approved by an opinion committee of Evercore.

Except as described above, the WPZ Conflicts Committee imposed no other restrictions or limitations on Evercore with respect to the investigations made or the procedures followed by Evercore in rendering its opinion. The Merger Consideration was determined through arm’s-length negotiations between the WPZ Conflicts Committee and Williams, and the WPZ Conflicts Committee approved the Merger Agreement and recommended the Merger Agreement to the WPZ Board for approval. Evercore provided advice to the WPZ Conflicts Committee during these negotiations. Evercore did not, however, recommend any specific Merger Consideration to the WPZ Conflicts Committee, the WPZ Board or Williams Partners or recommend that any specific Merger Consideration constituted the only appropriate consideration for the Merger. Evercore’s opinion was only one of many factors considered by the WPZ Conflicts Committee in evaluating the Merger and making its recommendation to the board of directors of the WPZ General Partner, and the opinion should not be viewed as determinative of the views of the WPZ Conflicts Committee with respect to the Merger.

Under the terms of Evercore’s engagement letter with the WPZ Conflicts Committee, Williams Partners agreed to pay Evercore a fee of $1,250,000 upon rendering its opinion, which was not contingent upon the conclusion of Evercore’s opinion or the consummation of the Merger. Evercore also received a fee of $250,000

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upon execution of its engagement letter with the WPZ Conflicts Committee, and Evercore will be entitled to receive an additional fee of $1,500,000 if the Merger is consummated. In addition, Williams Partners has agreed to reimburse Evercore for its reasonable out-of-pocket expenses (including legal fees, expenses and disbursements) incurred in connection with its engagement and to indemnify Evercore and any of its members, partners, officers, directors, advisors, representatives, employees, agents, affiliates and controlling persons, if any, against certain liabilities and expenses arising out of its engagement, or to contribute to payments which any of such persons might be required to make with respect to such liabilities.

Evercore and its affiliates engage in a wide range of activities for their own accounts and the accounts of customers. In connection with these businesses or otherwise, Evercore and its affiliates and/or their respective employees, as well as investment funds in which any of them may have a financial interest, may at any time, directly or indirectly, hold long or short positions and may trade or otherwise effect transactions for their own accounts or the accounts of customers, in debt or equity securities, senior loans and/or derivative products relating to Williams Partners, Williams and their respective affiliates and, accordingly, may at any time hold a long or short position in such securities or instruments.

During the past two years, no material relationship has existed between Evercore and its affiliates and Williams Partners, Williams or any of their respective affiliates pursuant to which compensation was received by Evercore or its affiliates as a result of such a relationship, other than WPZ Conflicts Committee’s December 2016 engagement of Evercore as its financial advisor with respect to Williams Partners’ issuance of WPZ Common Units to the WPZ General Partner in consideration for, among other things, the Incentive Distribution Rights Waiver (as defined below), for which services Evercore received total fees of $2,000,000 and reimbursement of certain expenses. Evercore may provide financial or other services to Williams Partners and/or Williams in the future and in connection with any such services may receive compensation. Evercore has not provided any services to Williams or any of its affiliates (other than the WPZ Conflicts Committee) in connection with the Merger.

Recommendation of the Williams Board and Its Reasons for the Merger

On May 16, 2018, the Williams Board determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, and in connection with the Merger, the Charter Amendment and Stock Issuance, are in the best interests of Williams and its stockholders, approved and declared advisable the Merger Agreement, the Charter Amendment, and the Stock Issuance, and resolved to submit the Charter Amendment and Stock Issuance to a vote of the Williams Stockholders and recommend approval of the adoption of the Charter Amendment and approval of the Stock Issuance.

The Williams Board considered many factors in making its determination and recommendation. The Williams Board consulted with its financial and legal advisors and viewed the following factors as being generally positive or favorable in coming to its determination and related recommendation:

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The following factors are generally negative or unfavorable in making a determination and recommendation with respect to the Merger:

After taking into account all of the factors set forth above, as well as others, the Williams Board concluded that the potential benefits of the Merger outweighed any negative or unfavorable considerations and determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, the Charter Amendment and the Stock Issuance, are in the best interests of Williams and its stockholders.

The foregoing discussion is not intended to be exhaustive, but is intended to address the material information and principal factors considered by the Williams Board in considering the Merger. In view of the

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number and variety of factors and the amount of information considered, the Williams Board did not find it practicable to, and did not make specific assessments of, quantify or otherwise assign relative weights to, the specific factors considered in reaching its determination. In addition, the Williams Board did not undertake to make any specific determination as to whether any particular factor, or any aspect of any particular factor, was favorable or unfavorable to its ultimate determination, and individual members of the Williams Board may have given different weights to different factors. The Williams Board made its recommendation based on the totality of information presented to, and the investigation conducted by, the Williams Board. It should be noted that certain statements and other information presented in this section are forward-looking in nature and, therefore, should be read in light of the factors discussed under the heading “Information Regarding Forward-Looking Statements.”

Opinion of Morgan Stanley — Financial Advisor to the Williams Board

Williams retained Morgan Stanley to provide it with financial advisory services in connection with the Merger and to provide a financial opinion to the Williams Board. Williams selected Morgan Stanley to act as its financial advisor based on Morgan Stanley’s qualifications, expertise and reputation and its knowledge of the business and affairs of Williams. On May 16, 2018, at a meeting of the Williams Board, Morgan Stanley rendered its oral opinion, subsequently confirmed by delivery of a written opinion, dated May 16, 2018, that, as of such date and based upon and subject to the various assumptions made, procedures followed, matters considered and qualifications and limitations on the scope of review undertaken by Morgan Stanley as set forth in the written opinion, the Merger Consideration to be paid by Williams pursuant to the Merger Agreement was fair from a financial point of view to Williams.

The full text of the written opinion of Morgan Stanley delivered to the Williams Board, dated as of May 16, 2018, is attached as Annex C to this joint consent statement/proxy statement/prospectus and is incorporated herein by reference in its entirety. Williams Stockholders should read Morgan Stanley’s opinion carefully and in its entirety for a discussion of the assumptions made, procedures followed, matters considered and qualifications and limitations on the scope of the review undertaken by Morgan Stanley in rendering its opinion. This summary is qualified in its entirety by reference to the full text of such opinion. Morgan Stanley’s opinion was directed to the Williams Board, in its capacity as such, and addressed only whether the Merger Consideration to be paid by Williams pursuant to the Merger Agreement was fair from a financial point of view to Williams as of the date of such opinion. Morgan Stanley’s opinion did not address any other aspects or implications of the Merger. Morgan Stanley’s opinion did not in any manner address the price at which the Williams Common Stock would trade following the consummation of the Merger or at any time, and Morgan Stanley expressed no opinion or recommendation to any holder of shares of Williams Common Stock as to how such holder should vote at the Williams Special Meeting or whether to take any other action with respect to the Merger.

For purposes of rendering its opinion, Morgan Stanley, among other things:

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Morgan Stanley assumed and relied upon, without independent verification, the accuracy and completeness of the information that was publicly available or supplied or otherwise made available to Morgan Stanley by Williams, and formed a substantial basis for its opinion. With respect to the financial projections of Williams and Williams Partners provided by the management of Williams and the information relating to certain strategic, financial and operational benefits anticipated from the Merger, prepared by the management of Williams, Morgan Stanley assumed, with the consent of Williams, that they had been reasonably prepared on bases reflecting the best currently available estimates and judgments of the management of Williams of the future financial performance of Williams and Williams Partners, including the potential impact of the Revised Policy Statement on Treatment of Income Taxes by the Federal Energy Regulatory Commission (issued March 15, 2018) (the “Policy Statement”) and the recent changes in the U.S. tax laws and regulations pursuant to the TCJA on the future financial performance of Williams and Williams Partners, as to which Morgan Stanley expressed no view or opinion. Morgan Stanley further noted that (i) the actual and estimated financial and operating performance and the share price data that Morgan Stanley reviewed for the companies with publicly traded equity securities that Morgan Stanley deemed to be relevant and (ii) the financial terms of certain acquisition transactions that Morgan Stanley deemed relevant might not, in whole or in part, reflect the potential impact of the Policy Statement or the TCJA. In addition, Morgan Stanley assumed that the Merger will be consummated in accordance with the terms set forth in the Merger Agreement without any waiver, amendment or delay of any terms or conditions, including, among other things, that the definitive Merger Agreement would not differ in any material respect from the draft thereof furnished to Morgan Stanley. Morgan Stanley assumed that in connection with the receipt of all the necessary governmental, regulatory or other approvals and consents required for the Merger, no delays, limitations, conditions or restrictions would be imposed that would have a material adverse effect on the contemplated benefits expected to be derived in the proposed Merger. Morgan Stanley noted that it is not a legal, tax, or regulatory advisor. Morgan Stanley noted that it is a financial advisor only and relied upon, without independent verification, the assessment of Williams and Williams’ legal, tax, or regulatory advisors with respect to legal, tax, or regulatory matters. Morgan Stanley did not perform any tax assessment in connection with the Merger. Morgan Stanley expressed no opinion with respect to the fairness of the amount or nature of the compensation to any of Williams Partners’ officers, directors or employees, or any class of such persons, relative to the consideration to be paid to the holders of the WPZ Common Units in the transaction. Morgan Stanley was not requested to make, and did not make, any independent valuation or appraisal of the assets or liabilities (contingent or otherwise) of Williams Partners or Williams, nor was Morgan Stanley furnished with any such valuations or appraisals. Morgan Stanley’s opinion was necessarily based on financial, economic, market and other conditions as in effect on, and the information made available to Morgan Stanley as of, the date of its opinion. Events occurring after the date of Morgan Stanley’s opinion may affect Morgan

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Stanley’s opinion and the assumptions used in preparing it, and Morgan Stanley did not assume any obligation to update, revise or reaffirm its opinion.

Summary of Financial Analyses of Morgan Stanley

The following is a summary of the material financial analyses performed by Morgan Stanley in connection with its oral opinion and the preparation of its written opinion to the Williams Board, both provided as of May 16, 2018. The following summary is not a complete description of the financial analyses performed and factors considered by Morgan Stanley in connection with its opinion, nor does the order of analyses described represent the relative importance or weight given to those analyses. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data as it existed on or before May 11, 2018. Some of these summaries of financial analyses include information presented in tabular format. In order to fully understand the financial analyses used by Morgan Stanley, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. The analyses listed in the tables and described below must be considered as a whole. Assessing any portion of such analyses and of the factors reviewed, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying Morgan Stanley’s opinion. Furthermore, mathematical analysis is not in itself a meaningful method of using the data referred to below.

In performing the financial analyses summarized below and in arriving at its opinion, at the direction of the Williams Board, Morgan Stanley utilized and relied upon certain financial projections relating to Williams Partners and Williams, provided by the management of Williams and which are described below. In addition, Morgan Stanley utilized and relied upon the number of issued and outstanding common units of Williams Partners and shares of common stock of Williams provided by management of Williams. For further information regarding the financial and operating projections, see the section entitled “The Merger — Unaudited Financial Projections of Williams and Williams Partners” beginning on page 48.

Comparative Companies Analysis

Using publicly available information, Morgan Stanley compared selected financial data of Williams Partners and Williams with similar data for selected publicly traded companies engaged in businesses which Morgan Stanley considered to be sufficiently analogous to Williams Partners or Williams.

For Williams Partners, the companies selected by Morgan Stanley (the “WPZ Peers”), were as follows:

For Williams, the companies selected by Morgan Stanley (the “WMB Peers”), were as follows:

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The companies selected as the WPZ Peers were selected because they have similar midstream asset profiles and are all publicly traded master limited partnerships. Those selected as WMB Peers have similar midstream asset profiles with significant trading liquidity and scale. The companies selected may be considered similar to Williams Partners and Williams based on the nature of their assets and operations; however, none of the companies selected is identical or directly comparable to Williams Partners or Williams, and certain of these companies may have characteristics that are materially different from those of Williams Partners and Williams. The analyses necessarily involve complex considerations and judgments concerning differences in financial and operational characteristics of the companies involved and other factors that could affect the companies differently than would affect Williams Partners or Williams.

For each company listed above, Morgan Stanley calculated and compared various financial multiples and ratios based on publicly available information as of May 11, 2018. For each of the following analyses performed by Morgan Stanley, estimated financial data for the selected companies were based on (except as otherwise noted) the Williams internal forecast provided to Morgan Stanley by Williams Management (the “WMB internal forecast”) (in the case of Williams and Williams Partners) and information obtained from S&P Capital IQ and broker estimates (“Wall Street consensus estimates”) (in the case of the other selected companies). The information Morgan Stanley calculated for each of the selected companies included:

Results of the analysis for Williams Partners and Williams, respectively, are as follows:

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Morgan Stanley also calculated the same financial multiples and ratios for Williams Partners at the market price as of May 11, 2018, based on the WMB internal forecast.