<PAGE>   1
    As filed with the Securities and Exchange Commission on October 19, 1999
                                                           Registration No. 333-
================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                             ----------------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                                 CELERITEK, INC.
             (Exact name of Registrant as specified in its charter)

             CALIFORNIA                                77-0057484
  (State or other jurisdiction of           (I.R.S. Employer Identification
   incorporation or organization)                       Number)

                              3236 SCOTT BOULEVARD
                          SANTA CLARA, CALIFORNIA 95054
                    (Address of principal executive offices)

                             ----------------------
                             1994 STOCK OPTION PLAN
                             ----------------------

                                 TAMER HUSSEINI
                                 CELERITEK, INC.
                              3236 SCOTT BOULEVARD
                          SANTA CLARA, CALIFORNIA 95054
                                 (408) 986-5060
            (Name, address and telephone number of agent for service)
                             ----------------------
                                    Copy to:
                               John V. Roos, Esq.
                     Wilson Sonsini Goodrich & Rosati, P.C.
                               650 Page Mill Road
                           Palo Alto, California 94304
                             ----------------------
===============================================================================

                         CALCULATION OF REGISTRATION FEE

===============================================================================
<TABLE>
<CAPTION>

                                                              Proposed Maximum Proposed Maximum    Amount of
                                              Amount to be    Offering Price      Aggregate      Registration
    Title of Securities to be Registered     Registered (1)   Per Share (2)    Offering Price(2)     Fee
-------------------------------------------------------------------------------------------------------------
<S>                                              <C>             <C>             <C>                <C>
Common Stock, no par value                       221,440         $5.1572         $1,142,009.14      $317.48
</TABLE>


----------

(1) Pursuant to Rule 429 of the Securities Act of 1933, as amended (the
    "Securities Act"), the prospectus delivered to participants under the
    Registrant's 1994 Stock Option Plan, as amended (the "1994 Plan"), also
    relates to an aggregate of 1,281,855 shares previously registered under Form
    S-8 Registration Nos. 333-2886 and 333-52037.

(2) The Proposed Maximum Offering Price Per Share was estimated in part pursuant
    to Rule 457(h) under the Securities Act, and, in part, pursuant to Rule
    457(c) under the Securities Act. With respect to 76,136 shares which are
    subject to outstanding options to purchase Common Stock under the 1994 Plan,
    the Proposed Maximum Offering Price Per Share was estimated pursuant to Rule
    457(h) under which Rule the per share price of options to purchase stock
    under an employee stock option plan may be estimated by reference to the
    exercise price of such options. The weighted average exercise price of the
    76,136 shares subject to outstanding options under the 1994 Plan to be
    registered is $4.085. With respect to 145,304 shares of Common Stock
    available for future grant under the 1994 Plan, the Proposed Maximum
    Offering Price Per Share was estimated pursuant to Rule 457(c) whereby the
    per share price was determined by reference to the average between the high
    and low price reported in the Nasdaq National Market on October 13, 1999,
    which average was $5.719. The number referenced above in the table entitled
    "Proposed Maximum Offering Price Per Share" represents a weighted average of
    the foregoing estimates calculated in accordance with Rules 457(h) and
    457(c).
================================================================================
<PAGE>   2



                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference

        Celeritek, Inc. (the "Company") hereby incorporates by reference in this
registration statement the following documents and information heretofore filed
with the Securities and Exchange Commission:

        (a) The Company's Annual Report on Form 10-K for the fiscal year ended
March 31, 1999, pursuant to Section 13 of the Securities Exchange Act of 1934,
as amended (the "Exchange Act").

        (b) The Company's Quarterly Report on Form 10-Q for the fiscal quarter
ended June 30, 1999, filed pursuant to Section 13 of the Exchange Act.

        (c) All other reports filed pursuant to Section 13(a) or 15(d) of the
Exchange Act since the end of the fiscal year covered by the registrant document
referred to in (a) above.

        (d) The description of the Company's Common Stock to be offered hereby
is contained in the Company's Registration Statement on Form 8-A filed with the
Securities and Exchange Commission on November 2, 1995 pursuant to Section 12(g)
of the Exchange Act, including any amendment or report filed for the purpose of
updating such description.

        All documents subsequently filed by the Company pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment to this registration statement which indicates that all
securities offered hereby have been sold or which deregisters all securities
remaining unsold, shall be deemed to be incorporated by reference in this
registration statement and to be a 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

        The Company's Articles of Incorporation limit the liability of directors
for monetary damages to the maximum extent permitted by California law. Such
limitation of liability has no effect on the availability of equitable remedies,
such as injunctive relief or rescission.

                                      II-1

<PAGE>   3

        The Company's Bylaws provide that the Company will indemnify its
directors and officers and may indemnify its employees and agents (other than
officers and directors) against certain liabilities to the fullest extent
permitted by California law. The Company is also empowered under its Bylaws to
enter into indemnification agreements with its directors and officers and to
purchase insurance on behalf of any person whom it is required or permitted to
indemnify. The Company has entered into indemnification agreements with each of
its current directors and officers which provide for indemnification of, and
advancement of expenses to, such persons to the greatest extent permitted by
California law, including by reason of action or inaction occurring in the past
and circumstances in which indemnification and advancement of expenses are
discretionary under California law. Insofar as indemnification for liabilities
arising under the Securities Act may be permitted to directors, officers or
persons controlling the Company pursuant to the foregoing provisions, the
Company has been informed that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is therefore unenforceable.

Item 7. Exemption From Registration Claimed

        Not applicable.

Item 8. Exhibits

         4.1*  1994 Stock Option Plan and form of Stock Option Agreement.

         5.1   Opinion of Wilson Sonsini Goodrich & Rosati, P.C., as to the
               legality of securities being registered.

        23.1   Consent of Ernst & Young LLP, Independent Auditors.

        23.2   Consent of Counsel (contained in Exhibit 5.1).

        24.1   Power of Attorney (see Page II-5).

---------

* Incorporated by reference to the exhibit filed with the Company's Registration
Statement on Form S-8 filed with the Securities and Exchange Commission on May
7, 1998.

                                      II-2

<PAGE>   4




Item 9. Undertakings

        (a) Rule 415 Offering

         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.

        (b) Filing incorporating subsequent Exchange Act documents by reference

        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 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.

        (c) Request for acceleration of effective date or filing of registration
statement on Form S-8

        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 Securities and Exchange 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.


                                      II-3

<PAGE>   5



                                   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 Santa Clara, State of California, on October 15,
1999.

                                   CELERITEK, INC.

                                   By:  /s/ Tamer Husseini
                                      __________________________________________
                                      Tamer Husseini, President, Chief Executive
                                      Officer and Chairman of the Board


                                      II-4

<PAGE>   6




                                POWER OF ATTORNEY

        KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Tamer Husseini and P. Michael Houlihan,
jointly and severally, his attorneys-in-fact, each with the power of
substitution, for him 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 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 below by the following persons in the
capacities and on the dates indicated.

<TABLE>
<CAPTION>
         Signature                                  Title                             Date
-------------------------------      --------------------------------------     ----------------
<S>                                  <C>                                        <C>
/s/ Tamer Husseini                   President, Chief Executive Officer and     October 15, 1999
-------------------------------      Chairman of the Board (Principal
(Tamer Husseini)                     Executive Officer)




/s/ P. Michael Houlihan              Chief Financial Officer (Principal         October 15, 1999
-------------------------------      Financial and Accounting Officer)
(P. Michael Houlihan)



/s/ Robert H. Gallagher              Director                                   October 15, 1999
-------------------------------
(Robert J. Gallagher)



/s/ Thomas W. Hubbs                  Director                                   October 15, 1999
-------------------------------
(Thomas W. Hubbs)



/s/ William D. Rasdal                Director                                   October 15, 1999
-------------------------------
(William D. Rasdal)



/s/ Charles P. Waite                 Director                                   October 15, 1999
-------------------------------
(Charles P. Waite)
</TABLE>

                                      II-5


<PAGE>   7




                                 CELERITEK, INC.

                       REGISTRATION STATEMENT ON FORM S-8

                                  EXHIBIT INDEX

  Exhibit
  Number    Description
  -------   -----------
     4.1*   1994 Stock Option Plan and form of Stock Option Agreement.

     5.1    Opinion of Wilson Sonsini Goodrich & Rosati, P.C., as to the
            legality of securities being registered.

    23.1    Consent of Ernst & Young LLP, Independent Auditors.

    23.2    Consent of Counsel (contained in Exhibit 5.1).

    24.1    Power of Attorney (see Page II-5).

--------

* Incorporated by reference to the exhibit filed with the Company's Registration
Statement on Form S-8 filed with the Securities and Exchange Commission on May
7, 1998.


                                      II-6
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 15763}]
{"company-data": {"conformed-name": "CELERITEK INC/CA", "cik": "0000919583", "assigned-sic": "3674", "irs-number": "770057484", "state-of-incorporation": "CA", "fiscal-year-end": "0331"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-89275", "film-number": "99730534"}, "business-address": {"street1": "3236 SCOTT BLVD", "city": "SANTA CLARA", "state": "CA", "zip": "95054", "phone": "4089865060"}, "mail-address": {"street1": "3236 SCOTT BLVD", "city": "SANTA CLARA", "state": "CA", "zip": "95054"}}
1
    As filed with the Securities and Exchange Commission on October 19, 1999
                                                           Registration No. 333-
================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                             ----------------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                                 CELERITEK, INC.
             (Exact name of Registrant as specified in its charter)

             CALIFORNIA                                77-0057484
  (State or other jurisdiction of           (I.R.S. Employer Identification
   incorporation or organization)                       Number)

                              3236 SCOTT BOULEVARD
                          SANTA CLARA, CALIFORNIA 95054
                    (Address of principal executive offices)

                             ----------------------
                             1994 STOCK OPTION PLAN
                             ----------------------

                                 TAMER HUSSEINI
                                 CELERITEK, INC.
                              3236 SCOTT BOULEVARD
                          SANTA CLARA, CALIFORNIA 95054
                                 (408) 986-5060
            (Name, address and telephone number of agent for service)
                             ----------------------
                                    Copy to:
                               John V. Roos, Esq.
                     Wilson Sonsini Goodrich & Rosati, P.C.
                               650 Page Mill Road
                           Palo Alto, California 94304
                             ----------------------
===============================================================================

                         CALCULATION OF REGISTRATION FEE

===============================================================================
Proposed Maximum Proposed Maximum    Amount of
                                              Amount to be    Offering Price      Aggregate      Registration
    Title of Securities to be Registered     Registered (1)   Per Share (2)    Offering Price(2)     Fee
-------------------------------------------------------------------------------------------------------------
Common Stock, no par value                       221,440         $5.1572         $1,142,009.14      $317.48
----------

(1) Pursuant to Rule 429 of the Securities Act of 1933, as amended (the
    "Securities Act"), the prospectus delivered to participants under the
    Registrant's 1994 Stock Option Plan, as amended (the "1994 Plan"), also
    relates to an aggregate of 1,281,855 shares previously registered under Form
    S-8 Registration Nos. 333-2886 and 333-52037.

(2) The Proposed Maximum Offering Price Per Share was estimated in part pursuant
    to Rule 457(h) under the Securities Act, and, in part, pursuant to Rule
    457(c) under the Securities Act. With respect to 76,136 shares which are
    subject to outstanding options to purchase Common Stock under the 1994 Plan,
    the Proposed Maximum Offering Price Per Share was estimated pursuant to Rule
    457(h) under which Rule the per share price of options to purchase stock
    under an employee stock option plan may be estimated by reference to the
    exercise price of such options. The weighted average exercise price of the
    76,136 shares subject to outstanding options under the 1994 Plan to be
    registered is $4.085. With respect to 145,304 shares of Common Stock
    available for future grant under the 1994 Plan, the Proposed Maximum
    Offering Price Per Share was estimated pursuant to Rule 457(c) whereby the
    per share price was determined by reference to the average between the high
    and low price reported in the Nasdaq National Market on October 13, 1999,
    which average was $5.719. The number referenced above in the table entitled
    "Proposed Maximum Offering Price Per Share" represents a weighted average of
    the foregoing estimates calculated in accordance with Rules 457(h) and
    457(c).
================================================================================
2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference

        Celeritek, Inc. (the "Company") hereby incorporates by reference in this
registration statement the following documents and information heretofore filed
with the Securities and Exchange Commission:

        (a) The Company's Annual Report on Form 10-K for the fiscal year ended
March 31, 1999, pursuant to Section 13 of the Securities Exchange Act of 1934,
as amended (the "Exchange Act").

        (b) The Company's Quarterly Report on Form 10-Q for the fiscal quarter
ended June 30, 1999, filed pursuant to Section 13 of the Exchange Act.

        (c) All other reports filed pursuant to Section 13(a) or 15(d) of the
Exchange Act since the end of the fiscal year covered by the registrant document
referred to in (a) above.

        (d) The description of the Company's Common Stock to be offered hereby
is contained in the Company's Registration Statement on Form 8-A filed with the
Securities and Exchange Commission on November 2, 1995 pursuant to Section 12(g)
of the Exchange Act, including any amendment or report filed for the purpose of
updating such description.

        All documents subsequently filed by the Company pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment to this registration statement which indicates that all
securities offered hereby have been sold or which deregisters all securities
remaining unsold, shall be deemed to be incorporated by reference in this
registration statement and to be a 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

        The Company's Articles of Incorporation limit the liability of directors
for monetary damages to the maximum extent permitted by California law. Such
limitation of liability has no effect on the availability of equitable remedies,
such as injunctive relief or rescission.

                                      II-1
3

        The Company's Bylaws provide that the Company will indemnify its
directors and officers and may indemnify its employees and agents (other than
officers and directors) against certain liabilities to the fullest extent
permitted by California law. The Company is also empowered under its Bylaws to
enter into indemnification agreements with its directors and officers and to
purchase insurance on behalf of any person whom it is required or permitted to
indemnify. The Company has entered into indemnification agreements with each of
its current directors and officers which provide for indemnification of, and
advancement of expenses to, such persons to the greatest extent permitted by
California law, including by reason of action or inaction occurring in the past
and circumstances in which indemnification and advancement of expenses are
discretionary under California law. Insofar as indemnification for liabilities
arising under the Securities Act may be permitted to directors, officers or
persons controlling the Company pursuant to the foregoing provisions, the
Company has been informed that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is therefore unenforceable.

Item 7. Exemption From Registration Claimed

        Not applicable.

Item 8. Exhibits

         4.1*  1994 Stock Option Plan and form of Stock Option Agreement.

         5.1   Opinion of Wilson Sonsini Goodrich & Rosati, P.C., as to the
               legality of securities being registered.

        23.1   Consent of Ernst & Young LLP, Independent Auditors.

        23.2   Consent of Counsel (contained in Exhibit 5.1).

        24.1   Power of Attorney (see Page II-5).

---------

* Incorporated by reference to the exhibit filed with the Company's Registration
Statement on Form S-8 filed with the Securities and Exchange Commission on May
7, 1998.

                                      II-2
4

Item 9. Undertakings

        (a) Rule 415 Offering

         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.

        (b) Filing incorporating subsequent Exchange Act documents by reference

        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 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.

        (c) Request for acceleration of effective date or filing of registration
statement on Form S-8

        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 Securities and Exchange 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.

                                      II-3
5

                                   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 Santa Clara, State of California, on October 15,
1999.

                                   CELERITEK, INC.

                                   By:  /s/ Tamer Husseini
                                      __________________________________________
                                      Tamer Husseini, President, Chief Executive
                                      Officer and Chairman of the Board

                                      II-4
6

                                POWER OF ATTORNEY

        KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Tamer Husseini and P. Michael Houlihan,
jointly and severally, his attorneys-in-fact, each with the power of
substitution, for him 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 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 below by the following persons in the
capacities and on the dates indicated.
Signature                                  Title                             Date
-------------------------------      --------------------------------------     ----------------
/s/ Tamer Husseini                   President, Chief Executive Officer and     October 15, 1999
-------------------------------      Chairman of the Board (Principal
(Tamer Husseini)                     Executive Officer)

/s/ P. Michael Houlihan              Chief Financial Officer (Principal         October 15, 1999
-------------------------------      Financial and Accounting Officer)
(P. Michael Houlihan)

/s/ Robert H. Gallagher              Director                                   October 15, 1999
-------------------------------
(Robert J. Gallagher)

/s/ Thomas W. Hubbs                  Director                                   October 15, 1999
-------------------------------
(Thomas W. Hubbs)

/s/ William D. Rasdal                Director                                   October 15, 1999
-------------------------------
(William D. Rasdal)

/s/ Charles P. Waite                 Director                                   October 15, 1999
-------------------------------
(Charles P. Waite)
II-5
7

                                 CELERITEK, INC.

                       REGISTRATION STATEMENT ON FORM S-8

                                  EXHIBIT INDEX

  Exhibit
  Number    Description
  -------   -----------
     4.1*   1994 Stock Option Plan and form of Stock Option Agreement.

     5.1    Opinion of Wilson Sonsini Goodrich & Rosati, P.C., as to the
            legality of securities being registered.

    23.1    Consent of Ernst & Young LLP, Independent Auditors.

    23.2    Consent of Counsel (contained in Exhibit 5.1).

    24.1    Power of Attorney (see Page II-5).

--------

* Incorporated by reference to the exhibit filed with the Company's Registration
Statement on Form S-8 filed with the Securities and Exchange Commission on May
7, 1998.

                                      II-6