[CHAPMAN AND CUTLER LLP LETTERHEAD]



                                                                     EXHIBIT 5.1

                                  June 2, 2006


Littelfuse, Inc.
800 East Northwest Highway
Des Plaines, Illinois  60016


         Re:                      Littelfuse, Inc.
                         Form S-8 Registration Statement
                           (1934 Act File No. 0-20388)

Gentlemen:

         We have acted as special counsel for Littelfuse, Inc. ("Littelfuse") in
connection with the registration statement on Form S-8 (the "Registration
Statement") of Littelfuse which is being filed with the Securities and Exchange
Commission on May 31, 2006, covering up to 1,250,000 shares of Littelfuse's
Common Stock, $.01 par value (the "Common Stock"), issuable upon the exercise of
options granted to participants under the Littelfuse, Inc. Equity Incentive
Compensation Plan (the "Plan").

         As such counsel, we have examined the Certificate of Incorporation and
Bylaws of Littelfuse, the Plan, the Registration Statement and such other
corporate documents and records and have made such other inquiries as we have
deemed necessary or advisable in order to enable us to render the opinions
hereinafter set forth.

         The Plan provides that shares of Common Stock issuable to participants
under the Plan may be authorized but unissued shares of Common Stock or issued
shares of Common Stock reacquired by Littelfuse.

         Based on the foregoing, we are of the opinion that when authorized but
unissued shares of Common Stock issuable to participants under the Plan have
been issued, sold and delivered pursuant to and as provided by the Plan, such
shares of Common Stock will be validly issued, fully paid and nonassessable.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                         Respectfully submitted,



                                         CHAPMAN AND CUTLER LLP