FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
Starboard Value LP
   2. Issuer Name and Ticker or Trading Symbol
QUANTUM CORP /DE/ [QTM] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
777 THIRD AVENUE, 18TH FLOOR		 3. Date of Earliest Transaction (Month/Day/Year)
10/09/2015
(Street)

NEW YORK, NY 10017		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
4.50% Convertible Senior Notes due 2017 (1) (2) $ 1.65 (3) 10/09/2015   P   $ 3,755,000     (4) 11/15/2017 Common Stock 2,279,903 $ 85 $ 22,715,000 I By Starboard Value and Opportunity Master Fund Ltd (5)
4.50% Convertible Senior Notes due 2017 (1) (2) $ 1.65 (3) 10/09/2015   P   $ 435,000     (4) 11/15/2017 Common Stock 264,117 $ 85 $ 4,695,000 I By Starboard Value and Opportunity S LLC (6)
4.50% Convertible Senior Notes due 2017 (1) (2) $ 1.65 (3) 10/09/2015   P   $ 245,000     (4) 11/15/2017 Common Stock 148,755 $ 85 $ 795,000 I By Starboard Value and Opportunity C LP (7)
4.50% Convertible Senior Notes due 2017 (1) (2) $ 1.65 (3) 10/09/2015   P   $ 565,000     (4) 11/15/2017 Common Stock 343,048 $ 85 $ 7,345,000 I By Managed Account of Starboard Value LP (8)

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Starboard Value LP
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    
Starboard Value GP LLC
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    
STARBOARD VALUE & OPPORTUNITY S LLC
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    
Starboard Principal Co LP
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    
Starboard Principal Co GP LLC
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    
STARBOARD VALUE & OPPORTUNITY MASTER FUND LTD
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    
Starboard Value & Opportunity C LP
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    
Starboard Value R LP
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    
Starboard Value R GP LLC
777 THIRD AVENUE
18TH FLOOR
NEW YORK, NY 10017		     X    

Signatures

 Starboard Value LP; By: Starboard Value GP LLC; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date
 Starboard Value and Opportunity Master Fund Ltd; By: Starboard Value LP; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date
 Starboard Value and Opportunity S LLC; By: Starboard Value LP; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date
 Starboard Value and Opportunity C LP; By: Starboard Value LP; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date
 Starboard Value GP LLC; By: Starboard Principal Co LP; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date
 Starboard Principal Co LP; By:Starboard Principal Co GP LLC; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date
 Starboard Principal Co GP LLC; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date
 Starboard Value R LP; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date
 Starboard Value R GP LLC; By: /s/ Jeffrey C. Smith, Authorized Signatory   10/13/2015
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) This Form 4 is filed jointly by Starboard Value and Opportunity Master Fund Ltd ("Starboard V&O Fund"), Starboard Value and Opportunity S LLC ("Starboard S LLC"), Starboard Value and Opportunity C LP ("Starboard C LP"), Starboard Value LP ("Starboard Value LP"), Starboard Value GP LLC ("Starboard Value GP"), Starboard Principal Co LP ("Principal Co"), Starboard Principal Co GP LLC ("Principal GP"), Starboard Value R LP ("Starboard R LP"), Starboard Value R GP LLC ("Starboard R GP"), Jeffrey C. Smith, Mark R. Mitchell and Peter A. Feld (collectively, the "Reporting Persons"). To enable all of the Reporting Persons to gain access to the Securities and Exchange Commission's electronic filing system (which only accepts a maximum of 10 joint filers per report), this report is the first of two identical reports relating to the same transactions being filed with the Securities and Exchange Commission.
(2) Each Reporting Person may be deemed to be a member of a Section 13(d) group that owns more than 10% of the Issuer's outstanding shares of Common Stock. Each Reporting Person disclaims beneficial ownership of the shares of Common Stock reported herein except to the extent of his or its pecuniary interest therein, and this report shall not be deemed to be an admission that any Reporting Person is the beneficial owner of such shares of Common Stock for purposes of Section 16 or for any other purpose.
(3) The notes are convertible at an initial conversion rate of 607.1645 shares of the Issuer's common stock per $1,000 principal amount of notes (representing an initial conversion price of approximately $1.65 per share of the Issuer's common stock), subject to adjustment in certain circumstances.
(4) The Reporting Persons may convert their notes at their option, at any time prior to the close of business on the business day immediately preceding November 15, 2017.
(5) Shares of Common Stock, including Shares underlying the notes, beneficially owned by Starboard V&O Fund. Starboard Value LP, as the investment manager of Starboard V&O Fund, may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by Starboard V&O Fund. Each of Starboard Value GP, as the general partner of Starboard Value LP, Principal Co, as a member of Starboard Value GP, Principal GP, as the general partner of Principal Co and Messrs. Smith, Mitchell and Feld as members of Principal GP and as members of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP, may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by Starboard V&O Fund.
(6) Shares of Common Stock, including Shares underlying the notes, beneficially owned by Starboard S LLC. Starboard Value LP, as the manager of Starboard S LLC, may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by Starboard S LLC. Each of Starboard Value GP, as the general partner of Starboard Value LP, Principal Co, as a member of Starboard Value GP, Principal GP, as the general partner of Principal Co and Messrs. Smith, Mitchell and Feld as members of Principal GP and as members of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP, may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by Starboard S LLC.
(7) Shares of Common Stock, including Shares underlying the notes, beneficially owned by Starboard C LP. Each of Starboard R LP, as the general partner of Starboard C LP, and Starboard R GP, as the general partner of Starboard R LP, may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by Starboard C LP. Starboard Value LP, as the investment manager of Starboard C LP, may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by Starboard C LP. Each of Starboard Value GP, as the general partner of Starboard Value LP, Principal Co, as a member of Starboard Value GP, Principal GP, as the general partner of Principal Co, and Messrs. Smith, Mitchell and Feld, as members of Principal GP and as members of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP, may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by Starboard C LP.
(8) Shares, including Shares underlying the notes, held in an account managed by Starboard Value LP. Starboard Value GP, as the general partner of Starboard Value LP, Principal Co, as a member of Starboard Value GP, Principal GP, as the general partner of Principal Co and Messrs. Smith, Mitchell and Feld as members of Principal GP and as members of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP, may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by Starboard Value LP.

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