EXHIBIT 5.1

                      [LETTERHEAD OF DAVIS POLK & WARDWELL]

                                NOVEMBER 19, 1997

The AES Corporation
1001 North 19th Street
Arlington, Virginia 22209

Ladies and Gentlemen:

   
         We have acted as counsel in connection with the Registration  Statement
on Form S-3 (the  "REGISTRATION  STATEMENT")  filed by the AES Corporation  (the
"Company")  with  the  Securities  and  Exchange   Commission  pursuant  to  the
Securities  Act of 1933,  as amended,  for the  registration  of the sale by the
Company from time to time of up to $1,500,000,000  aggregate principal amount of
senior debt securities, senior subordinated debt securities, junior subordinated
debt   securities  and  junior   subordinated   debt   securities  (the  "JUNIOR
SUBORDINATED DEBT TRUST  SECURITIES")  issued directly or to a Trust referred to
below  (collectively,  the "DEBT SECURITIES") of the Company,  common stock, par
value  $0.01 per share,  (the  "COMMON  STOCK")  of the  Company  and  preferred
securities  (the  "PREFERRED  SECURITIES") of AES Trust III AES Trust IV and AES
Trust V, each a statutory business trust created under the Business Trust Act of
the State of Delaware  (each,  a "TRUST" and,  collectively,  the  "TRUSTS") and
guarantees of the Preferred  Securities  by the Company (the  "GUARANTEES")  and
stock  purchase   contracts  to  purchase  Common  Stock  (the  "STOCK  PURCHASE
CONTRACTS") and stock purchase  units,  each  representing  ownership of a Stock
Purchase  Contract and Debt Securities or debt obligations of third parties (the
"STOCK PURCHASE UNITS"). The senior Debt Securities are to be issued pursuant to
an indenture  (the "SENIOR  DEBT  INDENTURE")  between the Company and the First
National Bank of Chicago,  as trustee.  The senior  subordinated Debt Securities
are to be issued  pursuant to an Indenture dated as of July 1, 1996 (the "SENIOR
SUBORDINATED DEBT INDENTURE") between the Company and The First National Bank of
CHICAGO,  as trustee.  The junior  subordinated Debt Securities are to be issued
pursuant to an Indenture (the "JUNIOR  SUBORDINATED DEBT INDENTURE") between the
Company  and The  First  National  Bank  of  Chicago,  as  trustee.  The  Junior
Subordinated  Debt Trust  Securities  are to be issued  pursuant to an indenture
(the "JUNIOR  SUBORDINATED  DEBT TRUST  INDENTURE")  between the Company the The
First National Bank of Chicago as trustee. The First National Bank of Chicago in
its capacity as trustee under the Senior Indenture, the Subordinated
    



                                       2


Indenture,  the  Junior  Subordinated  Indenture  is  referred  to herein as the
"TRUSTEE" and the Senior Indenture,  Subordinated Indenture, Junior Subordinated
Indenture  and the Junior  Subordinated  Debt Trust  Indenture  are  referred to
herein collectively as the "INDENTURES."

         We have examined originals or copies, certified or otherwise identified
to our  satisfaction,  of such  documents,  corporate  records,  certificates of
public  officials  and other  instruments  as we have deemed  necessary  for the
purposes of rendering this opinion.

         On the basis of the foregoing, we are of the opinion that:

         1.    When the Indentures and any supplemental  Indenture to be entered
     into in  connection  with the issuance of any Debt  Security have been duly
     authorized,  executed and  delivered  by the Trustee and the  Company,  the
     specific terms of a particular  Debt Security have been duly authorized and
     established  in  accordance  with the  applicable  Indenture  and such Debt
     Security  has been duly  authorized,  executed,  authenticated,  issued and
     delivered in accordance  with the  applicable  Indenture and the applicable
     underwriting or other agreement, such Debt Security will constitute a valid
     and binding  obligation of the Company,  enforceable in accordance with its
     terms,  except  as  (a)  the  enforceability  thereof  may  be  limited  by
     bankruptcy, insolvency, reorganization,  fraudulent transfer, moratorium or
     similar laws now are  hereinafter  in effect  relating to or affecting  the
     enforcement  of creditors'  rights  generally and (b) the  availability  of
     equitable  remedies  may be  limited  by  equitable  principles  of general
     applicability  (regardless of whether  considered in a proceeding at law or
     in equity).

         2.    Upon  designation   of   the  relative  rights,  preferences  and
     limitations  of any series of Preferred  Stock by the Board of Directors of
     the Company and the proper  filing with the Secretary of State of the State
     of  Delaware of a  Certificate  of  Designation  relating to such series of
     Preferred Stock, all necessary  corporate action on the part of the Company
     will have been taken to  authorize  the issuance and sale of such series of
     Preferred Stock proposed to be sold by the Company, and when such shares of
     Preferred  Stock are issued and delivered in accordance with the applicable
     underwriting  or other  agreement,  such shares of Preferred  Stock will be
     validly issued,  fully paid and  non-assessable,  enforceable in accordance
     with their terms,  except as (a) the enforceability  thereof may be limited
     by bankruptcy, insolvency, reorganization,  fraudulent transfer, moratorium
     or similar laws now or hereinafter  in effect  relating to or effecting the
     enforcement  of creditors'  rights  generally and (b) the  availability  of
     equitable



                                       3

     remedies may be limited by equitable  principles  of general  applicability
     (regardless of whether considered in a proceeding at law or in equity).

         3.    When  necessary  corporate  action on the part of the Company has
     been taken to  authorize  the  issuance  and sale of such  shares of Common
     Stock  proposed to be sold by the  Company,  and when such shares of Common
     Stock  are  issued  and  delivered  in  accordance   with  the   applicable
     underwriting  or other  agreement,  such  shares  of Common  Stock  will be
     validly issued, fully paid and non-assessable.

         4.    When the Guarantees  have  been  duly  authorized by the Company,
     the applicable Guarantee Agreement has been duly executed and delivered and
     the  Preferred  Securities  have  been duly  issued  and  delivered  by the
     applicable  Trust as  contemplated  by the  Registration  Statement and any
     prospectus  supplement  relating  thereto,  the Guarantees  will constitute
     valid and binding  obligations  of the Company,  enforceable  in accordance
     with their terms,  except as (a) the enforceability  thereof may be limited
     by bankruptcy, insolvency, reorganization,  fraudulent transfer, moratorium
     or similar laws now or hereinafter  in effect  relating to or affecting the
     enforcement  of creditors'  rights  generally and (b) the  availability  of
     equitable  remedies  may be  limited  by  equitable  principles  of general
     applicability  (regardless of whether  considered in a proceeding at law or
     in equity).

         5.    When the  Stock  Purchase Units and Stock Purchase Contracts have
     been duly  authorized  by the Company,  the  applicable  Purchase  Contract
     Agreement and Pledge  Agreement have been duly executed and delivered,  the
     Stock Purchase Units and Stock Purchase Contracts will constitute valid and
     binding  obligations of the Company,  enforceable in accordance  with their
     terms,  except  as  (a)  the  enforceability  thereof  may  be  limited  by
     bankruptcy, insolvency, reorganization,  fraudulent transfer, moratorium or
     similar laws now or  hereinafter  in effect  relating to or  affecting  the
     enforcement  of creditors'  rights  generally and (b) the  availability  of
     equitable  remedies  may be  limited  by  equitable  principles  of general
     applicability  (regardless of whether  considered in a proceeding at law or
     in equity).

         In connection with the opinions  expressed above, we have assumed that,
at or prior to the time of the delivery of any such  security,  (i) the Board of
Directors  shall  have  duly  established  the terms of such  security  and duly
authorized the issuance and sale of such security and such  authorization  shall
not have been modified or rescinded;  (ii) the Registration Statement shall have
been declared effective and such effectiveness shall not




                                       4

have been  terminated or rescinded;  and (iii) there shall not have occurred any
change in law affecting the validity or enforceability of such security. We have
also assumed that none of the terms of any security to be established subsequent
to the date hereof,  nor the issuance  and  delivery of such  security,  nor the
compliance  by the  Company  with the terms of such  security  will  violate any
applicable  law or will result in a violation of any provision of any instrument
or agreement then binding upon the Company,  or any  restriction  imposed by any
court or governmental body having jurisdiction over the Company.

         We are  members  of the Bar of the State of New York and the  foregoing
opinion is limited to the laws of the State of New York, the federal laws of the
Unites  States  of  America  and the  General  Corporation  Law of the  State of
Delaware.

         We hereby  consent to the  filing of this  opinion as an exhibit to the
Registration Statement. In addition, we consent to the reference to us under the
caption "Legal Matters" in the prospectus.

         This  opinion is rendered  solely to you in  connection  with the above
matter.  This  opinion  may not be relied  upon by you for any other  purpose or
relied  upon by or  furnished  to any other  person  without  our prior  written
consent.

                                            Very truly yours,



                                            /s/ Davis Polk & Wardwell