As filed with the Securities and Exchange Commission on May 6, 2009

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

Under

The Securities Act of 1933

KLA-TENCOR CORPORATION

(Exact name of registrant as specified in its charter)

One Technology Drive

Milpitas, California 95035

(Address, including zip code, of principal executive offices)

Amended and Restated 1997 Employee Stock Purchase Plan

(Full title of the Plan)

Brian M. Martin

Senior Vice President and General Counsel

KLA-Tencor Corporation

One Technology Drive

Milpitas, California 95035

(408) 875-3000

(Name, address including zip code, and telephone number,

including area code, of agent for service)

Indicate by check mark whether the registrant is a large accelerated filer, as accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

CALCULATION OF REGISTRATION FEE

INCORPORATION OF DOCUMENTS BY REFERENCE TO PRIOR REGISTRATION STATEMENT

This Registration Statement is filed for the purpose of registering 1,000,000 additional shares of Common Stock, $0.01 par value, of KLA-Tencor Corporation (the “Registrant”) for use in connection with the Registrant’s 1997 Amended and Restated Employee Stock Purchase Plan (the “Plan”). A Registration Statement on Form S-8 (No. 333-152864) that was filed with the Securities and Exchange Commission on August 7, 2008 (the “Prior Registration Statement”) relating to the Plan is effective. Accordingly, in accordance with General Instruction E to Form S-8, the Registrant hereby incorporates by reference herein the contents of the Prior Registration Statement.

PART II

Information Required in the Registration Statement

II-1

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Milpitas, State of California, on the 6th day of May, 2009.

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS:

That the undersigned officers and directors of KLA-Tencor Corporation, a Delaware corporation, do hereby constitute and appoint Mark P. Dentinger and Brian M. Martin or any one of them, the lawful attorney-in-fact and agent, each with full power and authority to do any and all acts and things and to execute any and all instruments which said attorney and agent determines may be necessary or advisable or required to enable said corporation to comply with the Securities Act of 1933, as amended, and any rules or regulations or requirements of the Securities and Exchange Commission in connection with this Registration Statement. Without limiting the generality of the foregoing power and authority, the powers granted include the power and authority to sign the names of the undersigned officers and directors in the capacities indicated below to this Registration Statement, to any and all amendments, both pre-effective and post-effective, and supplements to this Registration Statement, and to any and all instruments or documents filed as part of or in conjunction with this Registration Statement or amendments or supplements thereof, and each of the undersigned hereby ratifies and confirms all that said attorneys and agents, or any one of them, shall do or cause to be done by virtue hereof. This Power of Attorney may be signed in several counterparts.

IN WITNESS WHEREOF, each of the undersigned has executed this Power of Attorney as of the date indicated.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

II-2

II-3

EXHIBIT INDEX