<PAGE>   1

     As filed with the Securities and Exchange Commission on July 21, 1998
                                                    Registration No.____________
================================================================================

                       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)

<TABLE>
<S>                                                      <C>       
           DELAWARE                                           94-2805249
(State or Other Jurisdiction of                             (I.R.S. Employer
 Incorporation or Organization)                           Identification Number)
</TABLE>


                              901 SAN ANTONIO ROAD
                               PALO ALTO, CA 94303
                        (Address, including zip code, of
                    Registrant's Principal Executive Offices)

                 RED CAPE SOFTWARE, INC. 1996 STOCK OPTION PLAN
                            (FULL TITLE OF THE PLAN)

                                SCOTT G. MCNEALY
                                    PRESIDENT
                             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:
                              David J. Segre, Esq.
                              Daniel R. Mitz, Esq.
                        WILSON SONSINI GOODRICH & ROSATI
                            Professional Corporation
                               650 PAGE MILL ROAD
                           PALO ALTO, CALIFORNIA 94304
                                 (650) 493-9300


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

<PAGE>   2

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                                                         Proposed
                                                 Proposed Maximum         Maximum          Amount of
   Title of Securities            Amount to be   Offering Price Per  Aggregate Offering   Registration
     to be Registered             Registered(#)       Share               Price               Fee
----------------------------      -------------  ------------------  ------------------   ------------
<S>                                <C>           <C>                 <C>                  <C>  
Common Stock of the                16,647           $0.85 (1)           $14,150.00          $4.20
Company to be issued upon
exercise of options granted
under the Red Cape
Software, Inc. 1996 Stock
Option Plan
</TABLE>

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

(1)      Calculated pursuant to Rule 457(h)(1) under the Securities Act of 1933,
         as amended (the "Act"), based on an exercise price of $0.85.


<PAGE>   3

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


ITEM 3. INFORMATION INCORPORATED BY REFERENCE.

        There are hereby incorporated by reference into 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, as amended on Form
               10-K/A, for the year ended June 30, 1997, 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 28, 1997, December 28, 1997, and March 29, 1998,
               respectively, filed pursuant to Section 13(a) of the Exchange
               Act, and amended Quarterly Reports on Form 10-Q for the quarters
               ended September 28, 1997, December 28, 1997, and March 29, 1998,
               respectively, filed pursuant to Section 13(a) and (b) of the
               Exchange Act on July 17, 1998.

        3.     The Registrant's Registration Statement on Form 8-A relating to
               the 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 relating to
               the Company's Common Share Purchase Rights filed pursuant
               to Section 12(b) of the Exchange Act on on May 22, 1989, as
               amended.

        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 DIRECTORS 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

                                        2

<PAGE>   4



agent of the Company or is or was serving 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      Red Cape Software, Inc. 1996 Stock Option 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 5).

</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 purpose 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.

               (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.


                                        3

<PAGE>   5



        (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 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 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.

                                   SIGNATURES


        Pursuant to the requirements of the Securities Act of 1933, the
registrant, Sun Microsystems, Inc., 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 July 20, 1998.

                                  Sun Microsystems, Inc.


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



                                        4

<PAGE>   6

                                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
(including post-effective 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,      July 20, 1998
-----------------------------          President and Chief Executive
Scott G. McNealy                       Officer (Principal Executive Officer)


/s/ MICHAEL E. LEHMAN                  Vice President, Corporate Resources      July 20, 1998
-----------------------------          and Chief Financial Officer
Michael E. Lehman                      (Principal Financial Officer)

/s/ GEORGE REYES                       Vice President and Controller            July 20, 1998
-----------------------------          (Principal Accounting Officer)
George Reyes

                                       Director                                 July   , 1998
-----------------------------
L. John Doerr


/s/ JUDITH L. ESTRIN                   Director                                 July 20, 1998
-----------------------------
Judith L. Estrin


/s/ ROBERT J. FISHER                   Director                                 July 20, 1998
-----------------------------
Robert J. Fisher


/s/ ROBERT L. LONG                     Director                                 July 20, 1998
-----------------------------
Robert L. Long


/s/ M. KENNETH OSHMAN                  Director                                 July 20, 1998
-----------------------------
M. Kenneth Oshman


/s/ A. MICHAEL SPENCE                  Director                                 July 20, 1998
-----------------------------
A. Michael Spence

</TABLE>

                                        5

<PAGE>   7

                                         INDEX TO EXHIBITS

<TABLE>
<CAPTION>
EXHIBIT
NUMBER                         DESCRIPTION 
------   ----------------------------------------------------------------------
<S>      <C>                    
4.1      Red Cape Software, Inc. 1996 Stock Option 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 5).

</TABLE>
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 15434}]
{"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": "333-59503", "film-number": "98669193"}, "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 July 21, 1998
                                                    Registration No.____________
================================================================================

                       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                                           94-2805249
(State or Other Jurisdiction of                             (I.R.S. Employer
 Incorporation or Organization)                           Identification Number)
901 SAN ANTONIO ROAD
                               PALO ALTO, CA 94303
                        (Address, including zip code, of
                    Registrant's Principal Executive Offices)

                 RED CAPE SOFTWARE, INC. 1996 STOCK OPTION PLAN
                            (FULL TITLE OF THE PLAN)

                                SCOTT G. MCNEALY
                                    PRESIDENT
                             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:
                              David J. Segre, Esq.
                              Daniel R. Mitz, Esq.
                        WILSON SONSINI GOODRICH & ROSATI
                            Professional Corporation
                               650 PAGE MILL ROAD
                           PALO ALTO, CALIFORNIA 94304
                                 (650) 493-9300

================================================================================
2

                         CALCULATION OF REGISTRATION FEE
Proposed
                                                 Proposed Maximum         Maximum          Amount of
   Title of Securities            Amount to be   Offering Price Per  Aggregate Offering   Registration
     to be Registered             Registered(#)       Share               Price               Fee
----------------------------      -------------  ------------------  ------------------   ------------
Common Stock of the                16,647           $0.85 (1)           $14,150.00          $4.20
Company to be issued upon
exercise of options granted
under the Red Cape
Software, Inc. 1996 Stock
Option Plan
----------------------

(1)      Calculated pursuant to Rule 457(h)(1) under the Securities Act of 1933,
         as amended (the "Act"), based on an exercise price of $0.85.
3

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INFORMATION INCORPORATED BY REFERENCE.

        There are hereby incorporated by reference into 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, as amended on Form
               10-K/A, for the year ended June 30, 1997, 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 28, 1997, December 28, 1997, and March 29, 1998,
               respectively, filed pursuant to Section 13(a) of the Exchange
               Act, and amended Quarterly Reports on Form 10-Q for the quarters
               ended September 28, 1997, December 28, 1997, and March 29, 1998,
               respectively, filed pursuant to Section 13(a) and (b) of the
               Exchange Act on July 17, 1998.

        3.     The Registrant's Registration Statement on Form 8-A relating to
               the 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 relating to
               the Company's Common Share Purchase Rights filed pursuant
               to Section 12(b) of the Exchange Act on on May 22, 1989, as
               amended.

        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 DIRECTORS 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

                                        2
4

agent of the Company or is or was serving 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      Red Cape Software, Inc. 1996 Stock Option 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 5).
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 purpose 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.

               (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.

                                        3
5

        (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 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 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.

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, the
registrant, Sun Microsystems, Inc., 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 July 20, 1998.

                                  Sun Microsystems, Inc.

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

                                        4
6

                                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
(including post-effective 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,      July 20, 1998
-----------------------------          President and Chief Executive
Scott G. McNealy                       Officer (Principal Executive Officer)

/s/ MICHAEL E. LEHMAN                  Vice President, Corporate Resources      July 20, 1998
-----------------------------          and Chief Financial Officer
Michael E. Lehman                      (Principal Financial Officer)

/s/ GEORGE REYES                       Vice President and Controller            July 20, 1998
-----------------------------          (Principal Accounting Officer)
George Reyes

                                       Director                                 July   , 1998
-----------------------------
L. John Doerr

/s/ JUDITH L. ESTRIN                   Director                                 July 20, 1998
-----------------------------
Judith L. Estrin

/s/ ROBERT J. FISHER                   Director                                 July 20, 1998
-----------------------------
Robert J. Fisher

/s/ ROBERT L. LONG                     Director                                 July 20, 1998
-----------------------------
Robert L. Long

/s/ M. KENNETH OSHMAN                  Director                                 July 20, 1998
-----------------------------
M. Kenneth Oshman

/s/ A. MICHAEL SPENCE                  Director                                 July 20, 1998
-----------------------------
A. Michael Spence
5
7

                                         INDEX TO EXHIBITS
EXHIBIT
NUMBER                         DESCRIPTION 
------   ----------------------------------------------------------------------
4.1      Red Cape Software, Inc. 1996 Stock Option 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 5).