<PAGE>   1
     As filed with the Securities and Exchange Commission on April __, 2000
                                                      Registration No. 333-

================================================================================


                       SECURITIES AND EXCHANGE COMMISSION
                             Washington D.C. 20549

                                    FORM S-8

                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933


                             SUN MICROSYSTEMS, INC.
             (Exact name of Registrant as specified in its charter)

                    DELAWARE                           94-28905249
         (State or Other Jurisdiction                (I.R.S. Employer
       of Incorporation or Organization)          Identification Number)

                              901 San Antonio Road
                              Palo Alto, CA 94303
                                 (650) 960-1300
                        (Address, including zip code, of
                   Registrant's principal executive offices)

             INNOSOFT INTERNATIONAL, INC. 1992 STOCK INCENTIVE PLAN
             INNOSOFT INTERNATIONAL, INC. 1999 EQUITY INCENTIVE PLAN
                           (Full Title of the Plans)

                                Scott G. McNealy
                            Chief Executive Officer
                             SUN MICROSYSTEMS, INC.
                              901 San Antonio Road
                              Palo Alto, CA 94303
                                 (650) 960-1300
            (Name, address, including zip code and telephone number,
                   including area code, of agent for service)

                                    COPY TO:

                              Daniel R. Mitz, Esq.
                        WILSON SONSINI GOODRICH & ROSATI
                            Professional Corporation
                               650 Page Mill Road
                              Palo Alto, CA 94304
                                 (650) 493-9300


================================================================================


                                       1



<PAGE>   2
<TABLE>
<CAPTION>
                                   CALCULATION OF REGISTRATION FEE
------------------------------------------------------------------------------------------------------
                                                             Proposed
                                                              Maximum     Proposed
                                                 Amount      Offering      Maximum         Amount of
                                                 to be        Price       Aggregate       Registration
Title of Securities to be Registered           Registered   Per Share   Offering Price        Fee
------------------------------------------------------------------------------------------------------
<S>                                            <C>          <C>         <C>               <C>
Common Stock of the Company to be issued
upon exercise of options granted under the
Innosoft International, Inc. 1992 Stock        46,967     $85.1875(1)  $4,001,001        $1,056.26
Incentive Plan and the
Innosoft International, Inc. 1999 Equity        5,053     $85.1875(1)  $  430,452        $  113.64
Incentive Plan
                                               ------                  ----------        ---------
      Total                                    52,020                  $4,431,453        $1,169.90
------------------------------------------------------------------------------------------------------
</TABLE>

(1)  Computed in accordance with Rule 457(h)(1) under the Securities Act of
     1933 as amended, solely for the purpose of calculating the registration
     fee. Computation is based on the average of the high and low prices
     reported on the NASDAQ Stock Market for the five business days prior to
     April 27, 2000.
<PAGE>   3
                                    PART II:

                 INFORMATION REQUIRED IN REGISTRATION STATEMENT

ITEM 3.   INFORMATION INCORPORATED BY REFERENCE.

     There are hereby incorporated by reference in this Registration Statement
the following documents and information heretofore filed with the Securities
and Exchange Commission (the "Commission") by Sun Microsystems, Inc. (the
"Registrant"):

     1.   The Registrant's Annual Report on Form 10-K for the year ended June
30, 1999, filed pursuant to Section 13(a) of the Securities Exchange Act of
1934, as amended (the "Exchange Act").

     2.   The Registrant's Quarterly Reports on Form 10-Q for the quarters
ended September 26, 1999 and December 26, 1999, respectively, filed pursuant to
Section 13(a) of the Exchange Act.

     3.   The Registrant's Registration Statement on Form 8-A relating to the
Registrant's Common Stock, filed pursuant to Section 12(b) of the Exchange Act
on October 24, 1986, as amended.

     4.   The Registrant's Registration Statement on Form 8-A/A Amendment No. 8
relating to the Registrant's Common Share Purchase Rights filed pursuant to
Section 12(b) of the Exchange Act on April 27, 2000.

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

ITEM 4.   DESCRIPTION OF SECURITIES.

     Not applicable.

ITEM 5.   INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not applicable.

ITEM 6.   INDEMNIFICATION OF DIRECTIONS AND OFFICERS.

     Section 145 of the General Corporation Law of the State of Delaware, as
amended, provides that under certain circumstances a corporation may indemnify
any person who was or is a party or is threatened to be made a party to any
threatened, pending or completed action, suit or proceeding whether civil,
criminal, administrative or investigative, by reason of the fact that he or she
is or was a director, officer, employee or agent of the Company or is or was
serving


                                       3
<PAGE>   4
at its request in such capacity in another corporation or business association,
against expenses (including attorneys' fees), judgments, fines and amounts paid
in settlement actually and reasonably incurred by him or her in connection with
such action, suit or proceeding if he or she acted in good faith and in a manner
he or she reasonably believed to be in or not opposed to the best interests of
the Company and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his or her conduct was unlawful.

     Section 11 of the Restated Certificate of Incorporation of the Registrant
provides in effect that, subject to certain limited exceptions, the Registrant
shall indemnify its directors and officers to the extent authorized or permitted
by the General Corporation Law of the State of Delaware. The directors and
officers of the Registrant are insured under policies of insurance maintained by
the Company, subject to the limits of the policies, against certain losses
arising from any claims made against them by reason of being or having been such
directors or officers. Like indemnification and insurance is also provided to
those employees of the Registrant who serve as administrators of the Plan. In
addition, the Company has entered into contracts with certain of its directors
providing for indemnification of such persons by the Registrant to the full
extent authorized or permitted by law, subject to certain limited exceptions.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

        Not applicable.

ITEM 8. EXHIBITS.

<TABLE>
<CAPTION>
Number  Document
<S>     <C>
4.1     Innosoft International, Inc. 1992 Stock Incentive Plan.
4.2     Innosoft International, Inc. 1999 Equity Incentive Plan.
5.1     Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation,
        with respect to the legality of the securities being registered.
23.1    Consent of Counsel (Contained in Exhibit 5.1).
23.2    Consent of Ernst & Young LLP, Independent Auditors.
24.1    Power of Attorney (See page 7).

</TABLE>

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 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.

          (2)  That, for the purposes of determining any liability under the
Securities Act, 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.

                                       4









<PAGE>   5


          (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, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in this 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.

     (c)  Insofar as indemnification for liabilities arising under the
Securities Act 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 Commission such
indemnification is against public policy as expressed in the Securities 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 Securities Act and will be governed
by the final adjudication of such issue.


                                       5
<PAGE>   6
                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the
Registrant, Sun Microsystems, Inc., a corporation organized and existing under
the laws of the State of Delaware, 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 Palo Alto, State of
California, on April 26, 2000.


                                   SUN MICROSYSTEMS, INC.

                                   By: /s/  Michael E. Lehman
                                       -----------------------------------
                                       Michael E. Lehman
                                       Vice President, Corporate Resources
                                       and Chief Financial Officer






                                       6
<PAGE>   7
                               POWER OF ATTORNEY

     KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Scott G. McNealy and Michael E. Lehman,
jointly and severally, his or her attorneys-in-fact, each with the power of
substitution, for him or her in any and all capacities, to sign any amendments
to this Registration Statement on Form S-8 and to file the same, with exhibits
thereto and other documents in connection therewith, with the Securities and
Exchange Commission, hereby ratifying and confirming all that each of said
attorneys-in-fact, or his or her substitute or substitutes, may 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 dates indicated.

<TABLE>
<CAPTION>
SIGNATURE                     TITLE                                   DATE

<S>                           <C>                                     <C>
/s/ Scott G. McNealy          Chairman of the Board of Directors,     April 26, 2000
-------------------------     and Chief Executive Officer
Scott G. McNealy              (Principal Executive Officer)

/s/ Michael E. Lehman         Vice President, Corporate Resources     April 26, 2000
-------------------------     and Chief Financial Officer
Michael E. Lehman             (Principal Financial Officer)

/s/ Michael L. Popov          Vice President, Corporate Controller    April 26, 2000
-------------------------     (Principal Accounting Officer)
Michael L. Popov

/s/ James L. Barksdale        Director                                April 26, 2000
-------------------------
James L. Barksdale

                              Director                                April 26, 2000
-------------------------
L. John Doerr

                              Director                                April 26, 2000
-------------------------
Judith L. Estrin

/s/ Robert J. Fisher          Director                                April 26, 2000
-------------------------
Robert J. Fisher

/s/ Robert L. Long            Director                                April 26, 2000
-------------------------
Robert L. Long

/s/ M. Kenneth Oshman         Director                                April 26, 2000
-------------------------
M. Kenneth Oshman

/s/ Naomi O. Seligman         Director                                April 26, 2000
-------------------------
Naomi O. Seligman
</TABLE>

                                       7


<PAGE>   8
                               INDEX TO EXHIBITS
<TABLE>
<CAPTION>
EXHIBIT
NUMBER         DESCRIPTION
-------        -----------
<S>            <C>
4.1            Innosoft International, Inc. 1992 Stock Incentive Plan.
4.2            Innosoft International, Inc. 1999 Equity Incentive Plan.
5.1            Opinion of Wilson Sonsini Goodrich & Rosati, Professional
               Corporation, with respect to the legality of the securities being
               registered.
23.1           Consent of Counsel (Contained in Exhibit 5.1).
23.2           Consent of Ernst & Young LLP, Independent Auditors.
24.1           Power of Attorney (See page 7).
</TABLE>
                                       8
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 15592}]
{"company-data": {"conformed-name": "SUN MICROSYSTEMS INC", "cik": "0000709519", "assigned-sic": "3571", "irs-number": "942805249", "state-of-incorporation": "DE", "fiscal-year-end": "0630"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-35796", "film-number": "611093"}, "business-address": {"street1": "901 SAN ANTONIO RD", "city": "PALO ALTO", "state": "CA", "zip": "94303", "phone": "6509601300"}, "mail-address": {"street1": "901 SAN ANTONIO ROAD", "city": "PALO ALTO", "state": "CA", "zip": "94303"}}
1
     As filed with the Securities and Exchange Commission on April __, 2000
                                                      Registration No. 333-

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington D.C. 20549

                                    FORM S-8

                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933

                             SUN MICROSYSTEMS, INC.
             (Exact name of Registrant as specified in its charter)

                    DELAWARE                           94-28905249
         (State or Other Jurisdiction                (I.R.S. Employer
       of Incorporation or Organization)          Identification Number)

                              901 San Antonio Road
                              Palo Alto, CA 94303
                                 (650) 960-1300
                        (Address, including zip code, of
                   Registrant's principal executive offices)

             INNOSOFT INTERNATIONAL, INC. 1992 STOCK INCENTIVE PLAN
             INNOSOFT INTERNATIONAL, INC. 1999 EQUITY INCENTIVE PLAN
                           (Full Title of the Plans)

                                Scott G. McNealy
                            Chief Executive Officer
                             SUN MICROSYSTEMS, INC.
                              901 San Antonio Road
                              Palo Alto, CA 94303
                                 (650) 960-1300
            (Name, address, including zip code and telephone number,
                   including area code, of agent for service)

                                    COPY TO:

                              Daniel R. Mitz, Esq.
                        WILSON SONSINI GOODRICH & ROSATI
                            Professional Corporation
                               650 Page Mill Road
                              Palo Alto, CA 94304
                                 (650) 493-9300

================================================================================

                                       1
2
CALCULATION OF REGISTRATION FEE
------------------------------------------------------------------------------------------------------
                                                             Proposed
                                                              Maximum     Proposed
                                                 Amount      Offering      Maximum         Amount of
                                                 to be        Price       Aggregate       Registration
Title of Securities to be Registered           Registered   Per Share   Offering Price        Fee
------------------------------------------------------------------------------------------------------
Common Stock of the Company to be issued
upon exercise of options granted under the
Innosoft International, Inc. 1992 Stock        46,967     $85.1875(1)  $4,001,001        $1,056.26
Incentive Plan and the
Innosoft International, Inc. 1999 Equity        5,053     $85.1875(1)  $  430,452        $  113.64
Incentive Plan
                                               ------                  ----------        ---------
      Total                                    52,020                  $4,431,453        $1,169.90
------------------------------------------------------------------------------------------------------
(1)  Computed in accordance with Rule 457(h)(1) under the Securities Act of
     1933 as amended, solely for the purpose of calculating the registration
     fee. Computation is based on the average of the high and low prices
     reported on the NASDAQ Stock Market for the five business days prior to
     April 27, 2000.
3
                                    PART II:

                 INFORMATION REQUIRED IN REGISTRATION STATEMENT

ITEM 3.   INFORMATION INCORPORATED BY REFERENCE.

     There are hereby incorporated by reference in this Registration Statement
the following documents and information heretofore filed with the Securities
and Exchange Commission (the "Commission") by Sun Microsystems, Inc. (the
"Registrant"):

     1.   The Registrant's Annual Report on Form 10-K for the year ended June
30, 1999, filed pursuant to Section 13(a) of the Securities Exchange Act of
1934, as amended (the "Exchange Act").

     2.   The Registrant's Quarterly Reports on Form 10-Q for the quarters
ended September 26, 1999 and December 26, 1999, respectively, filed pursuant to
Section 13(a) of the Exchange Act.

     3.   The Registrant's Registration Statement on Form 8-A relating to the
Registrant's Common Stock, filed pursuant to Section 12(b) of the Exchange Act
on October 24, 1986, as amended.

     4.   The Registrant's Registration Statement on Form 8-A/A Amendment No. 8
relating to the Registrant's Common Share Purchase Rights filed pursuant to
Section 12(b) of the Exchange Act on April 27, 2000.

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

ITEM 4.   DESCRIPTION OF SECURITIES.

     Not applicable.

ITEM 5.   INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not applicable.

ITEM 6.   INDEMNIFICATION OF DIRECTIONS AND OFFICERS.

     Section 145 of the General Corporation Law of the State of Delaware, as
amended, provides that under certain circumstances a corporation may indemnify
any person who was or is a party or is threatened to be made a party to any
threatened, pending or completed action, suit or proceeding whether civil,
criminal, administrative or investigative, by reason of the fact that he or she
is or was a director, officer, employee or agent of the Company or is or was
serving

                                       3
4
at its request in such capacity in another corporation or business association,
against expenses (including attorneys' fees), judgments, fines and amounts paid
in settlement actually and reasonably incurred by him or her in connection with
such action, suit or proceeding if he or she acted in good faith and in a manner
he or she reasonably believed to be in or not opposed to the best interests of
the Company and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his or her conduct was unlawful.

     Section 11 of the Restated Certificate of Incorporation of the Registrant
provides in effect that, subject to certain limited exceptions, the Registrant
shall indemnify its directors and officers to the extent authorized or permitted
by the General Corporation Law of the State of Delaware. The directors and
officers of the Registrant are insured under policies of insurance maintained by
the Company, subject to the limits of the policies, against certain losses
arising from any claims made against them by reason of being or having been such
directors or officers. Like indemnification and insurance is also provided to
those employees of the Registrant who serve as administrators of the Plan. In
addition, the Company has entered into contracts with certain of its directors
providing for indemnification of such persons by the Registrant to the full
extent authorized or permitted by law, subject to certain limited exceptions.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

        Not applicable.

ITEM 8. EXHIBITS.
Number  Document
4.1     Innosoft International, Inc. 1992 Stock Incentive Plan.
4.2     Innosoft International, Inc. 1999 Equity Incentive Plan.
5.1     Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation,
        with respect to the legality of the securities being registered.
23.1    Consent of Counsel (Contained in Exhibit 5.1).
23.2    Consent of Ernst & Young LLP, Independent Auditors.
24.1    Power of Attorney (See page 7).
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 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.

          (2)  That, for the purposes of determining any liability under the
Securities Act, 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.

                                       4
5

          (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, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in this 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.

     (c)  Insofar as indemnification for liabilities arising under the
Securities Act 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 Commission such
indemnification is against public policy as expressed in the Securities 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 Securities Act and will be governed
by the final adjudication of such issue.

                                       5
6
                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the
Registrant, Sun Microsystems, Inc., a corporation organized and existing under
the laws of the State of Delaware, 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 Palo Alto, State of
California, on April 26, 2000.

                                   SUN MICROSYSTEMS, INC.

                                   By: /s/  Michael E. Lehman
                                       -----------------------------------
                                       Michael E. Lehman
                                       Vice President, Corporate Resources
                                       and Chief Financial Officer

                                       6
7
                               POWER OF ATTORNEY

     KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Scott G. McNealy and Michael E. Lehman,
jointly and severally, his or her attorneys-in-fact, each with the power of
substitution, for him or her in any and all capacities, to sign any amendments
to this Registration Statement on Form S-8 and to file the same, with exhibits
thereto and other documents in connection therewith, with the Securities and
Exchange Commission, hereby ratifying and confirming all that each of said
attorneys-in-fact, or his or her substitute or substitutes, may 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 dates indicated.
SIGNATURE                     TITLE                                   DATE
/s/ Scott G. McNealy          Chairman of the Board of Directors,     April 26, 2000
-------------------------     and Chief Executive Officer
Scott G. McNealy              (Principal Executive Officer)

/s/ Michael E. Lehman         Vice President, Corporate Resources     April 26, 2000
-------------------------     and Chief Financial Officer
Michael E. Lehman             (Principal Financial Officer)

/s/ Michael L. Popov          Vice President, Corporate Controller    April 26, 2000
-------------------------     (Principal Accounting Officer)
Michael L. Popov

/s/ James L. Barksdale        Director                                April 26, 2000
-------------------------
James L. Barksdale

                              Director                                April 26, 2000
-------------------------
L. John Doerr

                              Director                                April 26, 2000
-------------------------
Judith L. Estrin

/s/ Robert J. Fisher          Director                                April 26, 2000
-------------------------
Robert J. Fisher

/s/ Robert L. Long            Director                                April 26, 2000
-------------------------
Robert L. Long

/s/ M. Kenneth Oshman         Director                                April 26, 2000
-------------------------
M. Kenneth Oshman

/s/ Naomi O. Seligman         Director                                April 26, 2000
-------------------------
Naomi O. Seligman
7
8
                               INDEX TO EXHIBITS
EXHIBIT
NUMBER         DESCRIPTION
-------        -----------
4.1            Innosoft International, Inc. 1992 Stock Incentive Plan.
4.2            Innosoft International, Inc. 1999 Equity Incentive Plan.
5.1            Opinion of Wilson Sonsini Goodrich & Rosati, Professional
               Corporation, with respect to the legality of the securities being
               registered.
23.1           Consent of Counsel (Contained in Exhibit 5.1).
23.2           Consent of Ernst & Young LLP, Independent Auditors.
24.1           Power of Attorney (See page 7).
8