<PAGE>   1
      As filed with the Securities and Exchange Commission on May 16, 2000
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                 --------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                               ------------------

                                  PLEXUS CORP.
             (Exact name of registrant as specified in its charter)

               WISCONSIN                                          39-134447
    (State or other jurisdiction of                           (I.R.S. Employer
     incorporation or organization)                          Identification No.)

         55 JEWELERS PARK DRIVE
           NEENAH, WISCONSIN                                       54957
(Address of Principal Executive Offices)                         (Zip Code)

                               ------------------

                 PLEXUS CORP. 2000 EMPLOYEE STOCK PURCHASE PLAN
                            (Full title of the plan)

                               -------------------

             JOSEPH D. KAUFMAN                                 Copy to:
Vice President, Secretary and General Counsel             KENNETH V. HALLETT
                PLEXUS CORP.                              Quarles & Brady LLP
           55 Jewelers Park Drive                     411 East Wisconsin Avenue
               P.O. Box 156                           Milwaukee, Wisconsin 53202
       Neenah, Wisconsin 54957-0156
                     (Name and address of agent for service)

                                 (920) 722-3451
          (Telephone number, including area code, of agent for service)

                               -------------------



<PAGE>   2
                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
====================================================================================================================

                                                         PROPOSED           PROPOSED
                                                         MAXIMUM             MAXIMUM
TITLE OF SECURITIES TO BE        AMOUNT TO BE          OFFERING PRICE       AGGREGATE              AMOUNT OF
       REGISTERED                REGISTERED (1)         PER SHARE(2)      OFFERING PRICE(2)     REGISTRATION FEE
====================================================================================================================

<S>                              <C>                   <C>                <C>                   <C>
Common Stock, par value $.01     1,000,000 shares       $77.0625(2)          $77,062,500          $ 20,345.00
          per share
====================================================================================================================

  Preferred Stock Purchase              (3)                 (3)                  (3)                   (3)
           Rights
====================================================================================================================
</TABLE>
(1)           The Plan provides for the possible adjustment of the number, price
              and kind of shares covered by options granted or to be granted in
              the event of certain capital or other changes affecting the
              Registrant's Common Stock. This Registration Statement therefore
              covers, in addition to the above-stated 1,000,000 shares, an
              indeterminate number of shares that may become subject to the Plan
              by means of any such adjustment.

(2)           Pursuant to Rule 457(h), estimated solely for the purpose of
              computing the registration fee, based upon $77.0625 per share,
              which is the average of the high and low sales prices of the
              Registrant's Common Stock as reported in the Nasdaq National
              Market on May 10, 2000. The actual offering price will be
              determined in accordance with the terms of the Plan.

(3)           One right is issued in tandem with each share of Plexus common
              stock. The value attributable to the Preferred Stock Purchase
              Rights is reflected in the market price of the Common Stock to
              which the Rights are attached. Includes registration of shares of
              the Registrant's Preferred Stock and Common Stock underlying such
              rights.




<PAGE>   3
                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

       Information specified in Part I of Form S-8 (Items 1 and 2) will be sent
or given to plan participants as specified by Rule 428(b)(1) under the
Securities Act of 1933.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

       The following documents filed by Plexus Corp. (the "Registrant")
(Commission File No. 000-44824) with the Securities and Exchange Commission
pursuant to Section 13 of the Securities Exchange Act of 1934, as amended are
incorporated herein by reference:

       (a)     The Registrant's Annual Report on Form 10-K for the fiscal year
               ended September 30, 1999;

       (b)     The Registrant's Quarterly Reports on Form 10-Q for the
               quarterly periods ended December 31, 1999 and March 31, 2000;

       (c)     The Registrant's Current Report on Form 8-K dated April
               28, 2000;

       (d)     The description of the Common Stock in the Registration
               Statement on Form 8-A dated July 18, 1986, as amended by
               Amendment No. 2 thereto dated May 20, 1999; and

       (e)     The description of the Preferred Stock Purchase Rights in
               the Registration Statement on Form 8-A, dated August 17, 1998.

       All documents subsequently filed by the Registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the 1934 Act, prior to the filing of a
post-effective amendment which indicates that all securities offered hereby have
been sold or which deregisters all securities then remaining unsold, shall be
deemed to be incorporated by reference herein and to be a part hereof from the
date of the filing of such documents.

       Any statement contained in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes hereof to the extent that a statement contained herein or in any
other subsequently filed document which also is or is deemed to be incorporated
by reference herein modifies or supersedes such statement. Any statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part hereof.

ITEM 4. DESCRIPTION OF SECURITIES.

                                       1
<PAGE>   4
        Not applicable.  See Item 3(d) above.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

       The legality of the shares of Common Stock registered hereunder are being
passed on for the Registrant by Quarles & Brady LLP, the Registrant's legal
counsel.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

       The Registrant is incorporated under the Wisconsin Business Corporation
Law ("WBCL"). Under Section 180.0851(1) of the WBCL, the Registrant is required
to indemnify a director or officer, to the extent such person is successful on
the merits or otherwise in the defense of a proceeding, for all reasonable
expenses incurred in the proceeding if such person was a party because he or she
was a director or officer of the Registrant. In all other cases, the Registrant
is required by Section 180.0851(2) of the WBCL to indemnify a director or
officer against liability incurred in a proceeding to which such person was a
party because he or she was an officer or director of the Registrant, unless it
is determined that he or she breached or failed to perform a duty owed to the
Registrant and the breach or failure to perform constitutes: (i) a willful
failure to deal fairly with the Registrant or its shareholders in connection
with a matter in which the director or officer has a material conflict of
interest; (ii) a violation of criminal law, unless the director or officer had
reasonable cause to believe his or her conduct was lawful or no reasonable cause
to believe his or her conduct was unlawful; (iii) a transaction from which the
director or officer derived an improper personal profit; or (iv) willful
misconduct. Section 180.0858(1) of the WBCL provides that, subject to certain
limitations, the mandatory indemnification provisions do not preclude any
additional right to indemnification or allowance of expenses that a director or
officer may have under the Registrant's articles of incorporation, bylaws, a
written agreement or a resolution of the Board of Directors or shareholders.

       Section 180.0859 of the WBCL provides that it is the public policy of the
State of Wisconsin to require or permit indemnification, allowance of expenses
and insurance to the extent required or permitted under Sections 180.0850 to
180.0858 of the WBCL for any liability incurred in connection with a proceeding
involving a federal or state statute, rule or regulation regulating the offer,
sale or purchase of securities.

       Section 180.0828 of the WBCL provides that, with certain exceptions, a
director is not liable to a corporation, its shareholders, or any person
asserting rights on behalf of the corporation or its shareholders, for damages,
settlements, fees, fines, penalties or other monetary liabilities arising from a
breach of, or failure to perform, any duty resulting solely from his or her
status as a director, unless the person asserting liability proves that the
breach or failure to perform constitutes any of the four exceptions to mandatory
indemnification under Section 180.0851(2) referred to above.

       Under Section 180.0833 of the WBCL, directors of the Registrant against
whom claims are asserted with respect to the declaration of an improper dividend
or other distribution to shareholders to which they assented are entitled to
contribution from other directors who assented to such distribution and from
shareholders who knowingly accepted the improper distribution, as provided
therein.

                                       2
<PAGE>   5
       Article VIII of the Registrant's Bylaws contains provisions that
generally parallel the indemnification provisions of the WBCL and cover certain
procedural matters not dealt with in the WBCL. Directors and officers of the
Registrant are also covered by directors' and officers' liability insurance
under which they are insured (subject to certain exceptions and limitations
specified in the policy) against expenses and liabilities arising out of
proceedings to which they are parties by reason of being or having been
directors or officers.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

       Not applicable.

ITEM 8. EXHIBITS.

       See Exhibit Index following the signatures page in this Registration
Statement, which Exhibit Index is incorporated herein by reference.

ITEM 9. UNDERTAKINGS.

      (a) The undersigned Registrant hereby undertakes:

         (1)   To file, during any period in which offers or sales are
being made, a post-effective amendment to this Registration Statement:

               (i)   To include any  prospectus required by Section 10(a)(3) of
                     the Securities Act of 1933;

               (ii)  To reflect in the prospectus any facts or events arising
                     after the effective date of the Registration Statement (or
                     the most recent post-effective amendment thereof) which,
                     individually or in the aggregate, represent a fundamental
                     change in the information set forth in the Registration
                     Statement. Notwithstanding the foregoing, any increase or
                     decrease in volume of securities offered (if the total
                     dollar value of securities offered would not exceed that
                     which was registered) and any deviation from the low or
                     high end of the estimated maximum offering range may be
                     reflected in the form of prospectus filed with the
                     Commission pursuant to Rule 424(b) if, in the aggregate,
                     the changes in volume and price represent no more than a
                     20% change in the maximum aggregate offering price set
                     forth in the "Calculation of Registration Fee" table in the
                     effective Registration Statement;

               (iii) To include any material information with respect to the
                     plan of distribution not previously disclosed in the
                     Registration Statement or any material change to such
                     information in the Registration Statement;

         Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) of
this section do not apply if the Registration Statement is on Form S-3 or Form
S-8, and the information required to be

                                       3
<PAGE>   6
included in a post-effective amendment by those paragraphs is contained in
periodic reports filed by the Registrant with the Commission pursuant to Section
13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated
by reference in the Registration Statement.

         (2) That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

    (b)  The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

    (h)  Reference is made to the indemnification provisions described in
Item 6 of this Registration Statement.

         Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the Registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.


                                       4
<PAGE>   7
                                   SIGNATURES

       Pursuant to the requirements of the Securities Act of 1933, 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 Neenah, State of Wisconsin, on May 16, 2000.

                                       PLEXUS CORP.
                                       (Registrant)

                                       By: /s/ PETER STRANDWITZ
                                          -------------------------------------
                                            Peter Strandwitz,
                                            Chairman and Chief Executive Officer


                               ------------------

                                POWER OF ATTORNEY

       KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Peter Strandwitz, John L. Nussbaum and Joseph D.
Kaufman, and each of them, his true and lawful attorneys-in-fact and agents,
with full power of substitution and resubstitution, for him and in his name,
place and stead, in any and all capacities, to sign any and all amendments
(including post-effective amendments) to this Registration Statement, and to
file the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, and any other regulatory
authority, granting unto said attorneys-in-fact and agents, and each of them,
full power and authority to do and perform each and every act and thing
requisite and necessary to be done in and about the premises, as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents or any of them, or their
substitutes, may lawfully do or cause to be done by virtue hereof.

                              --------------------

       Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.*
<TABLE>
<S>                                                         <C>
              /s/ PETER STRANDWITZ                                        /s/ DEAN A. FOATE
-----------------------------------------------------       ---------------------------------------------
Peter Strandwitz, Chairman, Chief Executive Office          Dean A. Foate, Director
and Director (Principal Executive Officer)

             /s/ JOHN L. NUSSBAUM                                        /s/ HAROLD R. MILLER
-----------------------------------------------------       ---------------------------------------------
John L. Nussbaum, President, Chief Operating Officer        Harold R. Miller, Director
and Director

             /s/ THOMAS B. SABOL                                         /s/ THOMAS J. PROSSER
-----------------------------------------------------       ---------------------------------------------
Thomas B. Sabol, Chief Financial Officer (Principal         Thomas J. Prosser, Director
Financial Officer)

                /s/ LISA M. KELLEY                                      /s/ AGUSTIN A. RAMIREZ
-----------------------------------------------------       ---------------------------------------------
Lisa M. Kelley, Treasurer and Principal Accounting          Agustin A. Ramirez, Director
Officer

                /s/ DAVID J. DRURY                                       /s/ JAN K. VER HAGEN
-----------------------------------------------------       ---------------------------------------------
David J. Drury, Director                                    Jan K. Ver Hagen, Director
</TABLE>

              *Each of these signatures is affixed as of May 16, 2000.


                                      S-1
<PAGE>   8
                                  PLEXUS CORP.
                               (THE "REGISTRANT")
                          (COMMISSION FILE NO. 0-14553)

                                  EXHIBIT INDEX
                                       TO
                         FORM S-8 REGISTRATION STATEMENT
<TABLE>
<CAPTION>

EXHIBIT                  DESCRIPTION              INCORPORATED HEREIN BY                  FILED HEREWITH
NUMBER                                                  REFERENCE TO

<S>            <C>                               <C>                                      <C>
4.1            Restated Articles of              Exhibit 3(i) to Plexus' Annual
               Incorporation of Plexus Corp.,    Report on Form 10-K for the
               as amended through August         year ended September 30, 1998.
               13, 1998

4.2            Bylaws of Plexus Corp., as        Exhibit 3(ii) to Plexus' Quarterly
               amended through November 14,      Report on Form 10-Q for the
               1996                              quarter ended September 30,
                                                 1996.

4.3            Shareholder Rights Plan dated     Exhibit 4.1 to the Registrant's
               as of August 13, 1998 between     Current Report on Form 8-K
               the Registrant and Firstar Trust  dated August 13, 1998.
               Co.

5              Opinion of Counsel                                                               X

23.1           Consent of                                                                       X
               PricewaterhouseCoopers LLP

23.2           Consent of Counsel                                                    Contained in Opinion
                                                                                     filed as Exhibit 5

23.3           Consent of Ernst & Young                                                        X
               LLP

24             Powers of Attorney                                                    Signature Page to this
                                                                                     Registration Statement
99             2000 Employee Stock Purchase      Exhibit A to the Registrant's
               Plan                              Proxy Statement dated January 17,
                                                 2000 for its Annual Meeting of
                                                 Shareholders on March 1, 2000.
</TABLE>




                                      EI-1
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{"company-data": {"conformed-name": "PLEXUS CORP", "cik": "0000785786", "assigned-sic": "3672", "irs-number": "391344447", "state-of-incorporation": "WI", "fiscal-year-end": "0930"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-37154", "film-number": "637775"}, "business-address": {"street1": "55 JEWELERS PARK DR", "city": "NEENAH", "state": "WI", "zip": "54957-0156", "phone": "9207223451"}, "mail-address": {"street1": "PLEXUS CORP", "street2": "55 JEWELERS PARK DR", "city": "NEENAH", "state": "WI", "zip": "54957-0156"}}
1
      As filed with the Securities and Exchange Commission on May 16, 2000
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                 --------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                               ------------------

                                  PLEXUS CORP.
             (Exact name of registrant as specified in its charter)

               WISCONSIN                                          39-134447
    (State or other jurisdiction of                           (I.R.S. Employer
     incorporation or organization)                          Identification No.)

         55 JEWELERS PARK DRIVE
           NEENAH, WISCONSIN                                       54957
(Address of Principal Executive Offices)                         (Zip Code)

                               ------------------

                 PLEXUS CORP. 2000 EMPLOYEE STOCK PURCHASE PLAN
                            (Full title of the plan)

                               -------------------

             JOSEPH D. KAUFMAN                                 Copy to:
Vice President, Secretary and General Counsel             KENNETH V. HALLETT
                PLEXUS CORP.                              Quarles & Brady LLP
           55 Jewelers Park Drive                     411 East Wisconsin Avenue
               P.O. Box 156                           Milwaukee, Wisconsin 53202
       Neenah, Wisconsin 54957-0156
                     (Name and address of agent for service)

                                 (920) 722-3451
          (Telephone number, including area code, of agent for service)

                               -------------------
2
                         CALCULATION OF REGISTRATION FEE
====================================================================================================================

                                                         PROPOSED           PROPOSED
                                                         MAXIMUM             MAXIMUM
TITLE OF SECURITIES TO BE        AMOUNT TO BE          OFFERING PRICE       AGGREGATE              AMOUNT OF
       REGISTERED                REGISTERED (1)         PER SHARE(2)      OFFERING PRICE(2)     REGISTRATION FEE
====================================================================================================================
Common Stock, par value $.01     1,000,000 shares       $77.0625(2)          $77,062,500          $ 20,345.00
          per share
====================================================================================================================

  Preferred Stock Purchase              (3)                 (3)                  (3)                   (3)
           Rights
====================================================================================================================
(1)           The Plan provides for the possible adjustment of the number, price
              and kind of shares covered by options granted or to be granted in
              the event of certain capital or other changes affecting the
              Registrant's Common Stock. This Registration Statement therefore
              covers, in addition to the above-stated 1,000,000 shares, an
              indeterminate number of shares that may become subject to the Plan
              by means of any such adjustment.

(2)           Pursuant to Rule 457(h), estimated solely for the purpose of
              computing the registration fee, based upon $77.0625 per share,
              which is the average of the high and low sales prices of the
              Registrant's Common Stock as reported in the Nasdaq National
              Market on May 10, 2000. The actual offering price will be
              determined in accordance with the terms of the Plan.

(3)           One right is issued in tandem with each share of Plexus common
              stock. The value attributable to the Preferred Stock Purchase
              Rights is reflected in the market price of the Common Stock to
              which the Rights are attached. Includes registration of shares of
              the Registrant's Preferred Stock and Common Stock underlying such
              rights.
3
                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

       Information specified in Part I of Form S-8 (Items 1 and 2) will be sent
or given to plan participants as specified by Rule 428(b)(1) under the
Securities Act of 1933.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

       The following documents filed by Plexus Corp. (the "Registrant")
(Commission File No. 000-44824) with the Securities and Exchange Commission
pursuant to Section 13 of the Securities Exchange Act of 1934, as amended are
incorporated herein by reference:

       (a)     The Registrant's Annual Report on Form 10-K for the fiscal year
               ended September 30, 1999;

       (b)     The Registrant's Quarterly Reports on Form 10-Q for the
               quarterly periods ended December 31, 1999 and March 31, 2000;

       (c)     The Registrant's Current Report on Form 8-K dated April
               28, 2000;

       (d)     The description of the Common Stock in the Registration
               Statement on Form 8-A dated July 18, 1986, as amended by
               Amendment No. 2 thereto dated May 20, 1999; and

       (e)     The description of the Preferred Stock Purchase Rights in
               the Registration Statement on Form 8-A, dated August 17, 1998.

       All documents subsequently filed by the Registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the 1934 Act, prior to the filing of a
post-effective amendment which indicates that all securities offered hereby have
been sold or which deregisters all securities then remaining unsold, shall be
deemed to be incorporated by reference herein and to be a part hereof from the
date of the filing of such documents.

       Any statement contained in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes hereof to the extent that a statement contained herein or in any
other subsequently filed document which also is or is deemed to be incorporated
by reference herein modifies or supersedes such statement. Any statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part hereof.

ITEM 4. DESCRIPTION OF SECURITIES.

                                       1
4
        Not applicable.  See Item 3(d) above.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

       The legality of the shares of Common Stock registered hereunder are being
passed on for the Registrant by Quarles & Brady LLP, the Registrant's legal
counsel.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

       The Registrant is incorporated under the Wisconsin Business Corporation
Law ("WBCL"). Under Section 180.0851(1) of the WBCL, the Registrant is required
to indemnify a director or officer, to the extent such person is successful on
the merits or otherwise in the defense of a proceeding, for all reasonable
expenses incurred in the proceeding if such person was a party because he or she
was a director or officer of the Registrant. In all other cases, the Registrant
is required by Section 180.0851(2) of the WBCL to indemnify a director or
officer against liability incurred in a proceeding to which such person was a
party because he or she was an officer or director of the Registrant, unless it
is determined that he or she breached or failed to perform a duty owed to the
Registrant and the breach or failure to perform constitutes: (i) a willful
failure to deal fairly with the Registrant or its shareholders in connection
with a matter in which the director or officer has a material conflict of
interest; (ii) a violation of criminal law, unless the director or officer had
reasonable cause to believe his or her conduct was lawful or no reasonable cause
to believe his or her conduct was unlawful; (iii) a transaction from which the
director or officer derived an improper personal profit; or (iv) willful
misconduct. Section 180.0858(1) of the WBCL provides that, subject to certain
limitations, the mandatory indemnification provisions do not preclude any
additional right to indemnification or allowance of expenses that a director or
officer may have under the Registrant's articles of incorporation, bylaws, a
written agreement or a resolution of the Board of Directors or shareholders.

       Section 180.0859 of the WBCL provides that it is the public policy of the
State of Wisconsin to require or permit indemnification, allowance of expenses
and insurance to the extent required or permitted under Sections 180.0850 to
180.0858 of the WBCL for any liability incurred in connection with a proceeding
involving a federal or state statute, rule or regulation regulating the offer,
sale or purchase of securities.

       Section 180.0828 of the WBCL provides that, with certain exceptions, a
director is not liable to a corporation, its shareholders, or any person
asserting rights on behalf of the corporation or its shareholders, for damages,
settlements, fees, fines, penalties or other monetary liabilities arising from a
breach of, or failure to perform, any duty resulting solely from his or her
status as a director, unless the person asserting liability proves that the
breach or failure to perform constitutes any of the four exceptions to mandatory
indemnification under Section 180.0851(2) referred to above.

       Under Section 180.0833 of the WBCL, directors of the Registrant against
whom claims are asserted with respect to the declaration of an improper dividend
or other distribution to shareholders to which they assented are entitled to
contribution from other directors who assented to such distribution and from
shareholders who knowingly accepted the improper distribution, as provided
therein.

                                       2
5
       Article VIII of the Registrant's Bylaws contains provisions that
generally parallel the indemnification provisions of the WBCL and cover certain
procedural matters not dealt with in the WBCL. Directors and officers of the
Registrant are also covered by directors' and officers' liability insurance
under which they are insured (subject to certain exceptions and limitations
specified in the policy) against expenses and liabilities arising out of
proceedings to which they are parties by reason of being or having been
directors or officers.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

       Not applicable.

ITEM 8. EXHIBITS.

       See Exhibit Index following the signatures page in this Registration
Statement, which Exhibit Index is incorporated herein by reference.

ITEM 9. UNDERTAKINGS.

      (a) The undersigned Registrant hereby undertakes:

         (1)   To file, during any period in which offers or sales are
being made, a post-effective amendment to this Registration Statement:

               (i)   To include any  prospectus required by Section 10(a)(3) of
                     the Securities Act of 1933;

               (ii)  To reflect in the prospectus any facts or events arising
                     after the effective date of the Registration Statement (or
                     the most recent post-effective amendment thereof) which,
                     individually or in the aggregate, represent a fundamental
                     change in the information set forth in the Registration
                     Statement. Notwithstanding the foregoing, any increase or
                     decrease in volume of securities offered (if the total
                     dollar value of securities offered would not exceed that
                     which was registered) and any deviation from the low or
                     high end of the estimated maximum offering range may be
                     reflected in the form of prospectus filed with the
                     Commission pursuant to Rule 424(b) if, in the aggregate,
                     the changes in volume and price represent no more than a
                     20% change in the maximum aggregate offering price set
                     forth in the "Calculation of Registration Fee" table in the
                     effective Registration Statement;

               (iii) To include any material information with respect to the
                     plan of distribution not previously disclosed in the
                     Registration Statement or any material change to such
                     information in the Registration Statement;

         Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) of
this section do not apply if the Registration Statement is on Form S-3 or Form
S-8, and the information required to be

                                       3
6
included in a post-effective amendment by those paragraphs is contained in
periodic reports filed by the Registrant with the Commission pursuant to Section
13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated
by reference in the Registration Statement.

         (2) That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

    (b)  The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

    (h)  Reference is made to the indemnification provisions described in
Item 6 of this Registration Statement.

         Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the Registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

                                       4
7
                                   SIGNATURES

       Pursuant to the requirements of the Securities Act of 1933, 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 Neenah, State of Wisconsin, on May 16, 2000.

                                       PLEXUS CORP.
                                       (Registrant)

                                       By: /s/ PETER STRANDWITZ
                                          -------------------------------------
                                            Peter Strandwitz,
                                            Chairman and Chief Executive Officer

                               ------------------

                                POWER OF ATTORNEY

       KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Peter Strandwitz, John L. Nussbaum and Joseph D.
Kaufman, and each of them, his true and lawful attorneys-in-fact and agents,
with full power of substitution and resubstitution, for him and in his name,
place and stead, in any and all capacities, to sign any and all amendments
(including post-effective amendments) to this Registration Statement, and to
file the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, and any other regulatory
authority, granting unto said attorneys-in-fact and agents, and each of them,
full power and authority to do and perform each and every act and thing
requisite and necessary to be done in and about the premises, as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents or any of them, or their
substitutes, may lawfully do or cause to be done by virtue hereof.

                              --------------------

       Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.*
/s/ PETER STRANDWITZ                                        /s/ DEAN A. FOATE
-----------------------------------------------------       ---------------------------------------------
Peter Strandwitz, Chairman, Chief Executive Office          Dean A. Foate, Director
and Director (Principal Executive Officer)

             /s/ JOHN L. NUSSBAUM                                        /s/ HAROLD R. MILLER
-----------------------------------------------------       ---------------------------------------------
John L. Nussbaum, President, Chief Operating Officer        Harold R. Miller, Director
and Director

             /s/ THOMAS B. SABOL                                         /s/ THOMAS J. PROSSER
-----------------------------------------------------       ---------------------------------------------
Thomas B. Sabol, Chief Financial Officer (Principal         Thomas J. Prosser, Director
Financial Officer)

                /s/ LISA M. KELLEY                                      /s/ AGUSTIN A. RAMIREZ
-----------------------------------------------------       ---------------------------------------------
Lisa M. Kelley, Treasurer and Principal Accounting          Agustin A. Ramirez, Director
Officer

                /s/ DAVID J. DRURY                                       /s/ JAN K. VER HAGEN
-----------------------------------------------------       ---------------------------------------------
David J. Drury, Director                                    Jan K. Ver Hagen, Director
*Each of these signatures is affixed as of May 16, 2000.

                                      S-1
8
                                  PLEXUS CORP.
                               (THE "REGISTRANT")
                          (COMMISSION FILE NO. 0-14553)

                                  EXHIBIT INDEX
                                       TO
                         FORM S-8 REGISTRATION STATEMENT
EXHIBIT                  DESCRIPTION              INCORPORATED HEREIN BY                  FILED HEREWITH
NUMBER                                                  REFERENCE TO
4.1            Restated Articles of              Exhibit 3(i) to Plexus' Annual
               Incorporation of Plexus Corp.,    Report on Form 10-K for the
               as amended through August         year ended September 30, 1998.
               13, 1998

4.2            Bylaws of Plexus Corp., as        Exhibit 3(ii) to Plexus' Quarterly
               amended through November 14,      Report on Form 10-Q for the
               1996                              quarter ended September 30,
                                                 1996.

4.3            Shareholder Rights Plan dated     Exhibit 4.1 to the Registrant's
               as of August 13, 1998 between     Current Report on Form 8-K
               the Registrant and Firstar Trust  dated August 13, 1998.
               Co.

5              Opinion of Counsel                                                               X

23.1           Consent of                                                                       X
               PricewaterhouseCoopers LLP

23.2           Consent of Counsel                                                    Contained in Opinion
                                                                                     filed as Exhibit 5

23.3           Consent of Ernst & Young                                                        X
               LLP

24             Powers of Attorney                                                    Signature Page to this
                                                                                     Registration Statement
99             2000 Employee Stock Purchase      Exhibit A to the Registrant's
               Plan                              Proxy Statement dated January 17,
                                                 2000 for its Annual Meeting of
                                                 Shareholders on March 1, 2000.
EI-1