content: <PAGE>   1
  
        As filed with the Securities and Exchange Commission on June 6, 2000
                                                                   File No. 333-
  ================================================================================
  
                         SECURITIES AND EXCHANGE COMMISSION
                               WASHINGTON, D.C. 20549
  
                                      FORM S-8
                               REGISTRATION STATEMENT
                                        UNDER
                             THE SECURITIES ACT OF 1933
  
                              FORRESTER RESEARCH, INC.
               (Exact name of registrant as specified in its charter)
  
              DELAWARE                                 04-2797789
      (State or other jurisdiction                  (I.R.S. Employer
    of incorporation or organization)              Identification No.)
  
  
                                400 Technology Square
                           Cambridge, Massachusetts 02139
                                   (617) 497-7090
            (Address of principal executive offices, including zip code)
  
                    AMENDED AND RESTATED FORRESTER RESEARCH, INC.
                             1996 EQUITY INCENTIVE PLAN
  
                             ---------------------------
  
                              (Full title of the plan)
  
                              SUSAN WHIRTY MAFFEI, ESQ.
                     Chief Financial Officer and General Counsel
                              Forrester Research, Inc.
                                400 Technology Square
                           Cambridge, Massachusetts 02139
                                   (617) 497-7090
                                (617) 868-0577 (Fax)
  
                    --------------------------------------------
  
   (Name, Address and Telephone Number, including Area Code, of Agent for Service)
  
                           CALCULATION OF REGISTRATION FEE
  <TABLE>
  <CAPTION>
  
   Title of Securities     Amount to be         PROPOSED MAXIMUM       PROPOSED MAXIMUM       AMOUNT OF
   to be registered        registered           OFFERING PRICE         AGGREGATE OFFERING     REGISTRATION
                                                PER SHARE(1)           PRICE(1)               FEE
  <S>                    <C>                     <C>                   <C>                   <C>
  COMMON STOCK,
  PAR VALUE $0.01        3,000,000 shares          $52.625               $157,875,000          $41,679
  </TABLE>
  
  (1) The offering price per share and the maximum aggregate offering price have
      been estimated solely for the purpose of determining the registration fee
      pursuant to Rule 457(h) on the basis of the average of the high and low
      prices of Forrester Research, Inc. Common Stock, par value $0.01 per share,
      reported on the Nasdaq National Market on May 30, 2000.
  
  
  ================================================================================
  
  <PAGE>   2
                                  EXPLANATORY NOTE
  
  
      This Registration Statement has been filed pursuant to General Instruction E
  on Form S-8, to register 3,000,000 additional securities to be offered pursuant
  to the Amended and Restated Forrester Research, Inc. 1996 Equity Incentive Plan
  (the "1996 Plan") of Forrester Research, Inc. (the "Registrant" or the
  "Company"). A registration statement on Form S-8 (No. 333- 22749), filed with
  the Commission on March 4, 1997 to register 5,800,000 shares of common stock
  offered pursuant to the 1996 Plan and the 1996 Stock Option Plan for
  Non-Employee Directors and a registration statement on Form S-8 (No. 333-96393),
  filed with the Commission on February 8, 2000 to register 5,000,000 shares of
  common stock offered pursuant to the 1996 Plan are currently effective and are
  hereby incorporated herein by reference.
  
      All references to shares of Company common stock have been adjusted to
  reflect the stock split effected in the form of a 100% stock dividend on
  February 7, 2000.
  
  
  
  
                                         -2-
  <PAGE>   3
  
  
  
                                     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 on Form S-8 to be signed on its behalf by the undersigned, thereunto
  duly authorized, in the City of Cambridge, The Commonwealth of Massachusetts, on
  this 6th day of June, 2000.
  
                                          FORRESTER RESEARCH, INC.
  
  
                                          By: /s/ Susan Whirty Maffei
                                             ----------------------------------
                                             Name:  Susan Whirty Maffei
                                             Title: Chief Financial Officer,
                                                    Vice President, Operations and
                                                    General Counsel
  
                                  POWER OF ATTORNEY
  
           Pursuant to the requirement of the Securities Act of 1933, this
  Registration Statement has been signed by the following persons in the
  capacities and on the dates indicated. Each person whose signature appears below
  hereby authorizes and constitutes George F. Colony and Susan Whirty Maffei,
  with full power of substitution, to execute in the name of and on behalf of such
  person any amendment (including any post-effective amendment) to this
  Registration Statement, and any subsequent registration statement for the same
  offering that may be filed under Rule 462(b) under the Securities Act, and to
  file the same, with exhibits thereto, and other documents in connection
  therewith, making such changes in this Registration Statement and any subsequent
  registration statement under Rule 462(b) as the person(s) so acting deems
  appropriate.
  
  Signature                       Title                           Date
  ---------                       -----                           ----
  
  /s/ George F. Colony
  -------------------------       Chief Executive Officer         June 6, 2000
  George F. Colony                and Chairman of the
                                  Board
  
  /s/ William M. Bluestein
  -------------------------       President, Chief Operating      June 6, 2000
  William M. Bluestein            Officer and Director
  
  
  
                                         -3-
  <PAGE>   4
  
  
  /s/ Robert M. Galford
  ----------------------          Director                        June 6, 2000
  Robert M. Galford
  
  
  /s/ George R. Hornig
  ----------------------          Director                        June 6, 2000
  George R. Hornig
  
  /s/ Michael H. Welles
  ----------------------          Director                        June 6, 2000
  Michael H. Welles
  
  /s/ Henk W. Broeders
  ----------------------          Director                        June 6, 2000
  Henk W. Broeders
  
  
  
  
                                         -4-
  <PAGE>   5
                                    EXHIBIT INDEX
  
  
  Number                  Title of Exhibit                                Page
  ------                  ----------------                                ----
  5                       Opinion of Ropes & Gray                          6
  
  23.1                    Consent of Arthur Andersen LLP                   7
  
  23.2                    Consent of Ropes & Gray
                          (contained in the opinion filed as
                          Exhibit 5 hereto)                                6
  
  24                      Power of Attorney (included as
                          part of the signature page filed
                          herewith)                                        3
  
  
                                         -5-
metadata_documents: [{"type": "S-8", "sequence": "1", "filename": "0001.txt", "description": "FORRESTER RESEARCH, INC.", "secsgml_size_bytes": 7737}]
metadata_filer: {"company-data": {"conformed-name": "FORRESTER RESEARCH INC", "cik": "0001023313", "assigned-sic": "8700", "irs-number": "042797789", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-38626", "film-number": "649692"}, "business-address": {"street1": "400 TECHNOLOGY SQUARE", "city": "CAMBRIDGE", "state": "MA", "zip": "02139", "phone": "6174977090"}, "mail-address": {"street1": "400 TECHNOLOGY SQUARE", "city": "CAMBRIDGE", "state": "MA", "zip": "02139"}}
text: 1
  
        As filed with the Securities and Exchange Commission on June 6, 2000
                                                                   File No. 333-
  ================================================================================
  
                         SECURITIES AND EXCHANGE COMMISSION
                               WASHINGTON, D.C. 20549
  
                                      FORM S-8
                               REGISTRATION STATEMENT
                                        UNDER
                             THE SECURITIES ACT OF 1933
  
                              FORRESTER RESEARCH, INC.
               (Exact name of registrant as specified in its charter)
  
              DELAWARE                                 04-2797789
      (State or other jurisdiction                  (I.R.S. Employer
    of incorporation or organization)              Identification No.)
  
                                400 Technology Square
                           Cambridge, Massachusetts 02139
                                   (617) 497-7090
            (Address of principal executive offices, including zip code)
  
                    AMENDED AND RESTATED FORRESTER RESEARCH, INC.
                             1996 EQUITY INCENTIVE PLAN
  
                             ---------------------------
  
                              (Full title of the plan)
  
                              SUSAN WHIRTY MAFFEI, ESQ.
                     Chief Financial Officer and General Counsel
                              Forrester Research, Inc.
                                400 Technology Square
                           Cambridge, Massachusetts 02139
                                   (617) 497-7090
                                (617) 868-0577 (Fax)
  
                    --------------------------------------------
  
   (Name, Address and Telephone Number, including Area Code, of Agent for Service)
  
                           CALCULATION OF REGISTRATION FEE
  Title of Securities     Amount to be         PROPOSED MAXIMUM       PROPOSED MAXIMUM       AMOUNT OF
   to be registered        registered           OFFERING PRICE         AGGREGATE OFFERING     REGISTRATION
                                                PER SHARE(1)           PRICE(1)               FEE
  COMMON STOCK,
  PAR VALUE $0.01        3,000,000 shares          $52.625               $157,875,000          $41,679
  (1) The offering price per share and the maximum aggregate offering price have
      been estimated solely for the purpose of determining the registration fee
      pursuant to Rule 457(h) on the basis of the average of the high and low
      prices of Forrester Research, Inc. Common Stock, par value $0.01 per share,
      reported on the Nasdaq National Market on May 30, 2000.
  
  ================================================================================
  2
                                  EXPLANATORY NOTE
  
      This Registration Statement has been filed pursuant to General Instruction E
  on Form S-8, to register 3,000,000 additional securities to be offered pursuant
  to the Amended and Restated Forrester Research, Inc. 1996 Equity Incentive Plan
  (the "1996 Plan") of Forrester Research, Inc. (the "Registrant" or the
  "Company"). A registration statement on Form S-8 (No. 333- 22749), filed with
  the Commission on March 4, 1997 to register 5,800,000 shares of common stock
  offered pursuant to the 1996 Plan and the 1996 Stock Option Plan for
  Non-Employee Directors and a registration statement on Form S-8 (No. 333-96393),
  filed with the Commission on February 8, 2000 to register 5,000,000 shares of
  common stock offered pursuant to the 1996 Plan are currently effective and are
  hereby incorporated herein by reference.
  
      All references to shares of Company common stock have been adjusted to
  reflect the stock split effected in the form of a 100% stock dividend on
  February 7, 2000.
  
                                         -2-
  3
  
                                     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 on Form S-8 to be signed on its behalf by the undersigned, thereunto
  duly authorized, in the City of Cambridge, The Commonwealth of Massachusetts, on
  this 6th day of June, 2000.
  
                                          FORRESTER RESEARCH, INC.
  
                                          By: /s/ Susan Whirty Maffei
                                             ----------------------------------
                                             Name:  Susan Whirty Maffei
                                             Title: Chief Financial Officer,
                                                    Vice President, Operations and
                                                    General Counsel
  
                                  POWER OF ATTORNEY
  
           Pursuant to the requirement of the Securities Act of 1933, this
  Registration Statement has been signed by the following persons in the
  capacities and on the dates indicated. Each person whose signature appears below
  hereby authorizes and constitutes George F. Colony and Susan Whirty Maffei,
  with full power of substitution, to execute in the name of and on behalf of such
  person any amendment (including any post-effective amendment) to this
  Registration Statement, and any subsequent registration statement for the same
  offering that may be filed under Rule 462(b) under the Securities Act, and to
  file the same, with exhibits thereto, and other documents in connection
  therewith, making such changes in this Registration Statement and any subsequent
  registration statement under Rule 462(b) as the person(s) so acting deems
  appropriate.
  
  Signature                       Title                           Date
  ---------                       -----                           ----
  
  /s/ George F. Colony
  -------------------------       Chief Executive Officer         June 6, 2000
  George F. Colony                and Chairman of the
                                  Board
  
  /s/ William M. Bluestein
  -------------------------       President, Chief Operating      June 6, 2000
  William M. Bluestein            Officer and Director
  
                                         -3-
  4
  
  /s/ Robert M. Galford
  ----------------------          Director                        June 6, 2000
  Robert M. Galford
  
  /s/ George R. Hornig
  ----------------------          Director                        June 6, 2000
  George R. Hornig
  
  /s/ Michael H. Welles
  ----------------------          Director                        June 6, 2000
  Michael H. Welles
  
  /s/ Henk W. Broeders
  ----------------------          Director                        June 6, 2000
  Henk W. Broeders
  
                                         -4-
  5
                                    EXHIBIT INDEX
  
  Number                  Title of Exhibit                                Page
  ------                  ----------------                                ----
  5                       Opinion of Ropes & Gray                          6
  
  23.1                    Consent of Arthur Andersen LLP                   7
  
  23.2                    Consent of Ropes & Gray
                          (contained in the opinion filed as
                          Exhibit 5 hereto)                                6
  
  24                      Power of Attorney (included as
                          part of the signature page filed
                          herewith)                                        3
  
                                         -5-