SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D
                                (Amendment No. 1)

                   Under the Securities Exchange Act of 1934*

                             Unisource Energy Corp.
--------------------------------------------------------------------------------
                                (Name of Issuer)

                           Common Stock, no par value
--------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    909205106
--------------------------------------------------------------------------------
                      (CUSIP Number of Class of Securities)

                                 Daniel S. Loeb
                                 Third Point LLC
                                 390 Park Avenue
                               New York, NY 10022
                                 (212) 224-7400
--------------------------------------------------------------------------------
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                   Copies to:
                            Michael A. Schwartz, Esq.
                          Willkie Farr & Gallagher LLP
                               787 Seventh Avenue
                             New York, NY 10019-6099
                                 (212) 728-8000

                                 January 3, 2006
--------------------------------------------------------------------------------
                          (Date of Event which Requires
                            Filing of this Schedule)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of ss.ss. 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the
following box:  [ ]

NOTE: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 240.13d-7 for other
parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).






                                  SCHEDULE 13D

--------------------------------------------------   ---------------------------
CUSIP No.  909205106                                 Page 2 of 11 Pages
--------------------------------------------------   ---------------------------

----------- --------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

            Daniel S. Loeb
----------- --------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

                                                                     (a) [ ]
                                                                     (b) [X]
----------- --------------------------------------------------------------------
    3       SEC USE ONLY

----------- --------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
----------- --------------------------------------------------------------------
    5       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e)  [ ]

----------- --------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            United States
--------------------- --------- ------------------------------------------------
                         7      SOLE VOTING POWER

                                0
NUMBER OF SHARES       --------- -----------------------------------------------
BENEFICIALLY OWNED       8      SHARED VOTING POWER
BY EACH REPORTING
PERSON WITH                     2,400,000
                      --------- ------------------------------------------------
                         9      SOLE DISPOSITIVE POWER

                                0
                      --------- ------------------------------------------------
                         10     SHARED DISPOSITIVE POWER

                                2,400,000
----------- --------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

            2,400,000
----------- --------------------------------------------------------------------
    12      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
            SHARES*     [ ]

----------- --------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            6.9%
----------- --------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            IN
----------- --------------------------------------------------------------------




                                  SCHEDULE 13D

--------------------------------------------------   ---------------------------
CUSIP No.  909205106                                 Page 3 of 11 Pages
--------------------------------------------------   ---------------------------

----------- --------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

            Third Point LLC                     I.D.# 13-3922602
----------- --------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

                                                                     (a) [ ]
                                                                     (b) [X]
----------- --------------------------------------------------------------------
    3       SEC USE ONLY

----------- --------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
----------- --------------------------------------------------------------------
    5       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e)  [ ]

----------- --------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            Delaware
--------------------- --------- ------------------------------------------------
                         7      SOLE VOTING POWER

                                0
NUMBER OF SHARES       --------- -----------------------------------------------
BENEFICIALLY OWNED       8      SHARED VOTING POWER
BY EACH REPORTING
PERSON WITH                     2,400,000
                      --------- ------------------------------------------------
                         9      SOLE DISPOSITIVE POWER

                                0
                      --------- ------------------------------------------------
                         10     SHARED DISPOSITIVE POWER

                                2,400,000
----------- --------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

            2,400,000
----------- --------------------------------------------------------------------
    12      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
            SHARES*     [ ]

----------- --------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            6.9%
----------- --------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            OO
----------- --------------------------------------------------------------------




                                  SCHEDULE 13D

--------------------------------------------------   ---------------------------
CUSIP No.  909205106                                 Page 4 of 11 Pages
--------------------------------------------------   ---------------------------

----------- --------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

            Third Point Offshore Fund Ltd.
----------- --------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

                                                                     (a) [ ]
                                                                     (b) [X]
----------- --------------------------------------------------------------------
    3       SEC USE ONLY

----------- --------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
----------- --------------------------------------------------------------------
    5       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e)  [ ]

----------- --------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            Cayman Islands
--------------------- --------- ------------------------------------------------
                         7      SOLE VOTING POWER

                                0
NUMBER OF SHARES       --------- -----------------------------------------------
BENEFICIALLY OWNED       8      SHARED VOTING POWER
BY EACH REPORTING
PERSON WITH                     1,466,200
                      --------- ------------------------------------------------
                         9      SOLE DISPOSITIVE POWER

                                0
                      --------- ------------------------------------------------
                         10     SHARED DISPOSITIVE POWER

                                1,466,200
----------- --------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

            1,466,200
----------- --------------------------------------------------------------------
    12      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
            SHARES*     [ ]

----------- --------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            4.2%
----------- --------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            OO
----------- --------------------------------------------------------------------






     This Amendment No. 1 (the "Amendment") amends the Schedule 13D filed on
February 7, 2005 (the "Schedule 13D") and is being filed on behalf of Third
Point LLC (f/k/a Third Point Management Company L.L.C.), a Delaware limited
liability company (the "Management Company"), Third Point Offshore Fund, Ltd., a
Cayman Islands limited liability exempted company (the "Offshore Fund"), and
Daniel S. Loeb, an individual ("Mr. Loeb", together with the Offshore Fund and
the Management Company, the "Reporting Persons"). The Schedule 13D relates to
the Common Stock, no par value, of Unisource Energy Corp., an Arizona
corporation (the "Company"). Unless the context otherwise requires, references
herein to "Common Stock" are to such Common Stock. The Management Company is the
investment manager or adviser to a variety of hedge funds and managed accounts
(such funds and accounts, collectively, including, but not limited to the
Offshore Fund, the "Funds"). Mr. Loeb is the Chief Executive Officer of the
Management Company. The Funds directly own the Common Stock to which this
Schedule 13D relates, and the Reporting Persons may be deemed to have beneficial
ownership over such Common Stock, by virtue of the authority granted to the
Management Company by the Funds to vote and to dispose of the securities held by
the Funds.

Item 2.  Identity and Background.

     Items 2(a) through 2(c) of the Schedule 13D is hereby amended by deleting
the entirety of the text and replacing it with the following, respectively:

     (a) This statement is filed by the Reporting Persons. Daniel S. Loeb is the
Chief Executive Officer of the Management Company and controls the Management
Company's business activities. The Management Company is organized as a limited
liability company under the laws of the State of Delaware. The Offshore Fund is
organized as a limited liability exempted company under the laws of the Cayman
Islands.

     (b) The address of the principal business and principal office of the
Management Company and Mr. Loeb is 390 Park Avenue, New York, NY 10022. The
address of the principal business and principal office of the Offshore Fund is
c/o Walkers SPV Limited, Walker House, Mary Street, P.O. Box 908GT, George Town,
Grand Cayman, Cayman Islands, British West Indies.

     (c) The principal business of the Management Company is to serve as
investment manager or adviser to the Funds. The principal business of Mr. Loeb
is to act as the Chief Executive Officer of the Management Company. The
principal business of the Offshore Fund is to invest and trade in securities.

                                       5



Item 3.  Source and Amount of Funds or Other Consideration.

     Item 3 of the Schedule 13D is hereby amended by deleting the entirety of
the text thereof and replacing it with the following:

     The Funds expended an aggregate of $69,288,636.45 of their own investment
capital to acquire the 2,400,000 shares of Common Stock currently held by them
(the "Shares"). The Offshore Fund expended an aggregate of $42,434,800.81 of its
own investment capital to acquire the 1,466,200 Shares currently held by it. In
each case, the Shares were acquired through open market purchases.

     The Funds effect purchases of securities primarily through margin accounts
maintained for them with Bear, Stearns Securities Corp. and Goldman, Sachs & Co.
(the "Primary Brokers") which may extend margin credit to the Funds as and when
required to open or carry positions in the margin accounts, subject to
applicable Federal margin regulations, stock exchange rules and the firm's
credit policies. In such instances, the positions held in the margin accounts
are pledged as collateral security for the repayment of debit balances in the
accounts.

Item 5.  Interest in Securities of the Issuer.

     Item 5 of the Schedule 13D is hereby amended by deleting the entirety of
the text thereof and replacing it with the following:

     (a) As of the date of this Amendment, the Management Company beneficially
owns 2,400,000 shares of Common Stock. The Management Company shares voting and
dispositive power over such holdings with Mr. Loeb and with the Funds. The
Shares represent 6.9% of the 34,731,206 shares of Common Stock outstanding at
November 2, 2005 as reported in the Company's Quarterly Report on Form 10-Q for
the fiscal quarter ended September 30, 2005, filed on November 4, 2005. The
percentages used herein and in the rest of this statement are calculated based
upon this number of outstanding shares.

     As of the date of this Amendment, the Offshore Fund directly beneficially
owns 1,466,200 shares of Common Stock, which represents 4.2% of the total Common
Stock outstanding.

     (b) The Management Company and Mr. Loeb share voting and dispositive power
over the 2,400,000 shares of Common Stock held by the Funds. The Management
Company, Mr. Loeb and the Offshore Fund share voting and dispositive power over
the 1,466,200 shares of Common Stock held by the Offshore Fund.

                                       6


     (c) Schedule A hereto sets forth certain information with respect to
transactions by the Funds, at the direction of the Reporting Persons, in the
Common Stock during the past sixty days.

     Schedule B hereto sets forth certain information with respect to
transactions by the Offshore Fund, at the direction of the Management Company
and Mr. Loeb, in the Common Stock during the past sixty days.

     All of the transactions set forth on Schedule A and Schedule B, except as
may be otherwise noted therein, were effected in open market purchases on the
New York Stock Exchange through the Primary Brokers.

     Except as set forth above and on Schedule A and Schedule B, during the last
sixty days there were no transactions in the Common Stock effected by the
Reporting Persons, nor, to the best of their knowledge, any of their directors,
executive officers, general partners or members.

     (d) Other than the Funds which directly hold the Shares, and except as set
forth in this Item 5, no person is known to have the right to receive or the
power to direct the receipt of dividends from, or the proceeds from the sale of,
such shares.

     (e) On June 6, 2005, Offshore Fund ceased to be the beneficial owner of
more than five percent of the Common Stock.


             [THE REMAINDER OF THIS PAGE LEFT INTENTIONALLY BLANK.]

                                       7




                                   Schedule A
                                   ----------

                          (Transactions by the Funds in
                    Common Stock during the past sixty days)


----------------------- -------------------- -------------------------------- -----------------------------------
         Date              Transaction                  Shares                        Price Per Share
----------------------- -------------------- -------------------------------- -----------------------------------
                                                                             
      11/30/2005                BUY                      14,800                            32.3300
----------------------- -------------------- -------------------------------- -----------------------------------
      11/30/2005               SELL                     (14,800)                           32.3300
----------------------- -------------------- -------------------------------- -----------------------------------
      1/03/2006                SELL                     (50,000)                           31.1590
----------------------- -------------------- -------------------------------- -----------------------------------
      1/04/2006                SELL                     (100,000)                          31.0096
----------------------- -------------------- -------------------------------- -----------------------------------
      1/04/2006                SELL                     (10,000)                           31.0279
----------------------- -------------------- -------------------------------- -----------------------------------

                                   Schedule B
                                   ----------

             (Transactions by only the Offshore Fund in Common Stock
                           during the past sixty days)



----------------------- -------------------- -------------------------------- -----------------------------------
         Date               Transaction                  Shares                        Price Per Share
----------------------- -------------------- -------------------------------- -----------------------------------
                                                                               
      11/30/2005               SELL                      (6,000)                           32.3300
----------------------- -------------------- -------------------------------- -----------------------------------
      1/03/2006                SELL                     (17,000)                           31.1590
----------------------- -------------------- -------------------------------- -----------------------------------
      1/04/2006                SELL                     (73,500)                           31.0096
----------------------- -------------------- -------------------------------- -----------------------------------
      1/04/2006                SELL                     (10,000)                           31.0279
----------------------- -------------------- -------------------------------- -----------------------------------






                                   SIGNATURES

     After reasonable inquiry and to the best of our knowledge and belief, the
undersigned certify that the information set forth in this statement is true,
complete and correct.


Dated: January 5, 2006


                                 THIRD POINT LLC


                                  By: /s/ Daniel S. Loeb
                                      ------------------------------------------
                                      Name:  Daniel S. Loeb
                                      Title: Chief Executive Officer



                                  THIRD POINT OFFSHORE FUND, LTD.


                                  By: /s/ Daniel S. Loeb
                                      ------------------------------------------
                                      Name:  Daniel S. Loeb
                                      Title: Director



                                  /s/ Daniel S. Loeb
                                  ----------------------------------------------
                                  Daniel S. Loeb



                [SIGNATURE PAGE TO AMENDMENT No.1 TO SCHEDULE 13D
                                 WITH RESPECT TO
                             UNISOURCE ENERGY CORP.]