UNITED STATES

SECURITIES EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D/A

Under the Securities Exchange Act of 1934

(Amendment No. 10)*

MORGAN STANLEY

(Name of Issuer)

Common Stock, par value $0.01 per Share

(Title of Class of Securities)

617446448

(CUSIP Number)

Tadashi Kuroda

Senior Managing Executive Officer

Mitsubishi UFJ Financial Group, Inc.

7-1, Marunouchi 2-chome

Chiyoda-ku, Tokyo 100-8330

Japan

81-3-3240-1111

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

April 6, 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 Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box  ¨.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Section 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, as amended (“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 statement (this “Amendment”) amends the Statement of Beneficial Ownership on Schedule 13D, filed on October 23, 2008, as amended by the first amendment thereto, filed on October 30, 2008, the second amendment thereto, filed on May 22, 2009, the third amendment thereto, filed on June 11, 2009, the fourth amendment thereto, filed on April 1, 2010, the fifth amendment thereto, filed on May 3, 2010, the sixth amendment thereto, filed on November 9, 2010, the seventh amendment thereto, filed on April 25, 2011, the eighth amendment thereto, filed on July 1, 2011, and the ninth amendment thereto, filed on October 4, 2013 (the “Schedule 13D”), by Mitsubishi UFJ Financial Group, Inc. (“MUFG”), a joint stock company incorporated in Japan, with respect to shares of common stock (the “Common Stock”) of Morgan Stanley, a Delaware corporation (the “Company”). Capitalized terms used and not defined in this Amendment shall have the meanings set forth in the Schedule 13D. Except as specifically provided herein, this Amendment does not modify any of the information previously reported in the Schedule 13D.

Item 3. Source and Amount of Funds or Other Consideration

In addition to the 432,017,152 shares of Common Stock held by MUFG directly, as of March 31, 2016, certain affiliates of MUFG held in the aggregate 3,299,928 shares of Common Stock (the “Managed Shares”) solely in a fiduciary capacity as the trustee of trust accounts or as the manager of investment funds, other investment vehicles and managed accounts. MUFG disclaims beneficial ownership of the Managed Shares.

Except as noted above, Item 3 of the Schedule 13D is hereby incorporated by reference herein.

Item 4. Purpose of Transaction

On April 6, 2016, MUFG and the Company entered into the Fourth Amendment to the Investor Agreement (the “Fourth Amendment to Investor Agreement”) to amend the standstill and preemptive right provisions in the Amended Investor Agreement previously disclosed in the Schedule 13D.

The Amended Investor Agreement provided that the standstill provisions will terminate, unless extended, upon the earlier of (a) April 13, 2016 or (b) the date on which MUFG’s Economic Interest Percentage is less than 10%. The Fourth Amendment to Investor Agreement extended this period so that the standstill provisions will terminate, unless extended, upon the earlier of (a) October 13, 2018 or (b) the date on which MUFG’s Economic Interest Percentage is less than 10%. The Amended Investor Agreement provided that the expiration date of the preemptive rights was April 13, 2016. The Fourth Amendment to Investor Agreement extended this expiration date to October 13, 2018.

The Fourth Amendment to Investor Agreement is filed as Exhibit 19 to this Amendment and is hereby incorporated by reference herein.

Except as noted above, Item 4 of the Schedule 13D is hereby incorporated by reference herein.

Item 5. Interest in Securities of the Issuer

(a) Rows (7) through (11) and (13) of the cover pages to this Amendment are hereby incorporated by reference. For purposes of calculating the percentages set forth in this Item 5, the number of shares outstanding is assumed to be 1,958,568,849 (which is the number of shares of Common Stock outstanding as of January 31, 2016, as reported by the Company in their annual report on Form 10-K for the year ended December 31, 2015).

As of April 7, 2016, MUFG beneficially owns 432,017,152 shares of Common Stock.

In addition, MUFG may be deemed to be the beneficial owner of the Managed Shares. MUFG disclaims beneficial ownership of the Managed Shares.

The shares of Common Stock beneficially owned by MUFG (if MUFG is deemed to have beneficial ownership over the Managed Shares) represent approximately 22.23% of the outstanding shares of Common Stock.

(b) Subject to the right of clients to withdraw their assets, including the Managed Shares managed by MUFG’s affiliates, MUFG has the sole power to vote or direct the vote and to dispose or to direct the disposition of shares of Common Stock beneficially owned by it as indicated in rows (7) through (11) and (13) of the cover pages to this Amendment.

(c) Except as described herein, neither MUFG nor, to its knowledge, any of its directors or executive officers has engaged in any transactions in shares of the Company’s Common Stock in the past 60 days except transactions in a fiduciary capacity as described under Item 3.

(d) No other person is known by MUFG to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, any shares of the Company’s securities beneficially owned by MUFG, except that, if MUFG is deemed to have beneficial ownership of the Managed Shares, dividends and the proceeds from the sale of Managed Shares will be the property of the customers for whom such Managed Shares are managed.

(e) Not applicable.

Item 7. Material to be Filed as Exhibits

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: April 7, 2016

MITSUBISHI UFJ FINANCIAL GROUP, INC.

Exhibit 19

Fourth Amendment to Investor Agreement

THIS FOURTH AMENDMENT TO THE INVESTOR AGREEMENT (this “Amendment”), dated as of April 6, 2016, is made by and between Morgan Stanley, a Delaware corporation (the “Company”), and Mitsubishi UFJ Financial Group, Inc., a joint stock company organized under the laws of Japan (the “Investor”).

W I T N E S S E T H:

WHEREAS, the Company and the Investor are parties to that certain Investor Agreement, dated as of October 13, 2008, and amended by the First Amendment to Investor Agreement, dated as of October 27, 2008, and amended and restated by the Amended and Restated Investor Agreement, dated as of June 30, 2011, and amended by the Third Amendment to Investor Agreement, dated as of October 3, 2013 (the Investor Agreement, as so amended and restated, the “Investor Agreement”); and

WHEREAS, the Company and the Investor have determined to further amend the Investor Agreement as set forth herein.

NOW THEREFORE, in consideration of the premises and of the respective representations, warranties, covenants and conditions contained herein, the parties hereto agree as follows:

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Please confirm that the foregoing correctly sets forth the agreement between us by signing in the space provided below for that purpose.

AGREED AND ACCEPTED:

[Signature Page to Fourth Amendment to Investor Agreement]