Keith Meister, Eric Mandelblatt Step Down from Williams Companies (WMB) Board

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Amendment No. 7)*

Under the Securities Exchange Act of 1934

THE WILLIAMS
COMPANIES, INC.

(Name of Issuer)

Common Stock, par value $1.00 per share

(Title of Class of Securities)

969457100

(CUSIP Number)

Keith Meister

Patrick J. Dooley, Esq.

Corvex Management LP

667
Madison Avenue

New York, New York 10065

(212) 474-6700

Eric W.
Mandelblatt

Soroban Capital Partners LP

444 Madison Avenue, 21st Floor

New York, New York 10022

(212) 314-1300

COPIES TO:

Jeffrey Kochian, Esq.

Akin Gump Strauss Hauer & Feld LLP

One Bryant Park

New
York, NY 10036

(212) 872-1000

Richard Brand

Cadwalader, Wickersham & Taft LLP

200 Liberty Street

New
York, NY 10281

(212) 504-5757

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

June 30, 2016

(Date of
Event which Requires Filing of this Statement)

If the filing person has
previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box   x.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule §240.13d-7
for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be
deemed to be filed for the purpose of Section 18 of the Securities Exchange Act of 1934 (Act) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act
(however, see the Notes).

This Amendment No. 7 supplements the information set forth in the Schedule 13D filed by Corvex Management
LP, Keith Meister, Soroban Master Fund LP, Soroban Capital Partners LLC, and Eric W. Mandelblatt with the United States Securities and Exchange Commission (the SEC) on December 16, 2013, as amended from time to time (as amended, the
Schedule 13D) relating to the shares of Common Stock, par value $1.00 per share (the Shares) of The Williams Companies, Inc., a Delaware corporation (the Issuer). Capitalized terms used but not defined herein
shall have the meanings ascribed to them in the Schedule 13D.

The information set forth in response to each separate Item below shall be deemed to be a
response to all Items where such information is relevant. The Schedule 13D is supplementally amended as follows.

This statement on Schedule 13D is filed jointly by the following entities and
persons, all of whom are together referred to herein as the Reporting Persons:

(a) Corvex Management LP, a Delaware limited partnership
(Corvex), and Keith Meister, a U.S. citizen (collectively, the Corvex Persons). This statement relates to Shares held for the account of certain private investment funds for which Corvex acts as investment adviser, including
Corvex Master Fund, LP, a Cayman Islands limited partnership, the general partner of which is controlled by Mr. Meister (collectively, the Corvex Funds). The general partner of Corvex is controlled by Mr. Meister. The principal
business of Corvex is serving as the investment adviser of the Corvex Funds, whose principal business is investing in securities. Mr. Meisters principal occupation is serving as the Managing Partner of Corvex. The principal business
address of each of Corvex and Mr. Meister is 667 Madison Avenue, New York, NY 10065.

(b) Soroban Master Fund LP, a Cayman Islands exempted limited
partnership (SMF Fund), Soroban Capital GP LLC, a Delaware limited liability company (SCGP LLC), Soroban Capital Partners LP, a Delaware limited partnership (formerly known as Soroban Capital Partners LLC) (SCP
LP), Soroban Capital Partners GP LLC, a Delaware limited liability company (SCP GP) and Eric W. Mandelblatt, a U.S. citizen (collectively, the Soroban Persons). This statement relates to Shares held for the account of
SMF Fund, a private investment fund for which SCP LP acts as investment manager. SCGP LLC is the general partner of SMF Fund and is controlled by Mr. Mandelblatt through his role as Managing Partner of SCGP LLC. SCP LP is controlled by
Mr. Mandelblatt through his role as Managing Partner of SCP GP, the general partner SCP LP. The principal business of SCP LP is serving as the investment manager of SMF Fund, whose principal business is investing in securities. The principal
business of SCGP is serving as the general partner of SMF Fund, and the principal business of SCP GP is serving as the general partner of SCP LP. The principal business of Mr. Mandelblatt is serving as Managing Partner of SCGP LLC and Managing
Partner of SCP GP. The principal business address of SMF Fund is Gardenia Court, Suite 3307, 45 Market Street, Camana Bay, Grand Cayman KY1-1103, Cayman Islands and the principal business address of SCGP LLC, SCP LP, SCP GP and Mr. Mandelblatt
is 444 Madison Avenue, 21st Floor, New York, NY 10022.

A joint filing agreement of the Corvex Persons and the Soroban Persons is attached hereto as
Exhibit 1.

During the last five years, none of the Reporting Persons has been convicted in a criminal proceeding (excluding traffic violations or
similar misdemeanors) or has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of,
or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Information
contained herein concerning each Corvex Person has been provided by each such Corvex Person and the Soroban Persons assume no responsibility for such information. Information contained herein concerning each Soroban Person has been provided by each
such Soroban Person and the Corvex Persons assume no responsibility for such information.

On June 30, 2016, Mr. Meister and Mr. Mandelblatt resigned from
the Board of Directors (the Board) of the Issuer. In connection with the resignations of Mr. Meister and Mr. Mandelblatt from the Board, each of Mr. Meister and Mr. Mandelblatt delivered a letter to the Board describing the
reasons for such resignations. A copy of the letter to the Board delivered by Mr. Meister is attached hereto as Exhibit 2 and is incorporated herein by reference. A copy of the letter to the Board delivered by Mr. Mandelblatt is attached
hereto as Exhibit 3 and is incorporated herein by reference.

As a result of such resignations, the previously disclosed Agreement referenced in
Item 6 was terminated.

The Reporting Persons intend to review their respective investment in the Issuer on a continuing basis and may from time to
time and at any time in the future depending on various factors, including, without limitation, the Issuers financial position and strategic direction, actions taken by the Board, price levels of the Shares, other investment opportunities
available to the Reporting Persons, conditions in the securities market and general economic and industry conditions, take such actions with respect to their respective investments in the Issuer as they deem appropriate, including, without
limitation: (i) acquiring additional Shares and/or other equity, debt, notes, other securities, or derivative or other instruments that are based upon or relate to the value of the Shares or the Issuer (collectively, Securities) of the
Issuer in the open market or otherwise; (ii) disposing of any or all of their Securities in the open market or otherwise; (iii) engaging in any hedging or similar transactions with respect to the Securities; or (iv) proposing or considering one or
more of the actions described in subsections (a) through (j) of Item 4 of Schedule 13D.

(a) (b) The Corvex Persons may be deemed to be the
beneficial owner of 41,682,960 Shares, which collectively represent approximately 5.6% of the Issuers outstanding Shares. Corvex may be deemed to have sole power to vote and sole power to dispose of 41,682,960 Shares. By virtue of his position
as control person of the general partner of Corvex, Mr. Meister may be considered to beneficially own such Shares.

The Soroban Persons may be deemed
to be the beneficial owner of 21,000,000 Shares, which represent approximately 2.8% of the Issuers outstanding Shares. Each of the Soroban Persons may be deemed to have shared power to vote and dispose of such Shares.

The aggregate Shares reported as beneficially owned by the Corvex Persons and the Soroban Persons is 62,682,960 Shares, which collectively represent
approximately 8.4% of the Issuers outstanding Shares.

The percentages calculated in the immediately foregoing paragraph and in the paragraphs above
are calculated based on a total of 750,569,517 Shares outstanding as of May 19, 2016, as reported in the Form S-4 filed with the SEC by Energy Transfer Corp LP on May 25, 2016.

The filing of this Schedule 13D shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any securities covered by
the Schedule 13D except to the extent expressly noted herein.

(c) There have been no transactions with respect to the Shares during the sixty days prior
to the date hereof by any of the Reporting Persons.

(d) Except as set forth below, no person is known to have the right to receive, or the power to
direct the receipt of dividends from, or proceeds from the sale of, the Shares beneficially owned by any of the Reporting Persons, other than the Reporting Persons themselves.

The limited partners of (or investors in) each of the private investment funds for which Corvex or its affiliates acts as general partner and/or investment
adviser have the right to participate in the receipt of dividends from, or proceeds from the sale of, the Shares held for the accounts of their respective funds in accordance with their respective limited partnership interests (or investment
percentages) in their respective funds.

The limited partners of (or investors in) each of the private investment funds for which SCP LP or its affiliates
acts as general partner, managing member and/or investment manager have the right to participate in the receipt of dividends from, or proceeds from the sale of, the Shares held for the accounts of their respective funds in accordance with their
respective limited partnership interests, limited liability company interests or investment percentages in their respective funds.

(e) Not applicable.

As a
result of the resignation of Mr. Meister and Mr. Mandelblatt from the Board effective June 30, 2016, the previously disclosed Agreement among the Issuer and certain of the Reporting Persons dated February 25, 2014, was
terminated.

All previously disclosed European-style cash-settled call options held by SMF Fund have expired. None of the previously disclosed
European-style cash-settled call options gave SMF Fund direct or indirect voting or investment control over any securities of the Issuer and did not permit SMF Fund to exercise such cash-settled call options and receive Shares of the Issuer.

SIGNATURES

After reasonable inquiry and to the best of its or his knowledge and belief, each of the undersigned certifies that the information set forth in this
statement is true, complete and correct.