Exhibit 5(a)




                               September 21, 2001

FirstEnergy Corp.
76 South Main Street
Akron, Ohio  44308


                   Re: REGISTRATION STATEMENT ON FORM S-3
                       ----------------------------------

Dear Ladies and Gentlemen:

         I am Associate General Counsel for FirstEnergy Corp., an Ohio
corporation (the "COMPANY"). In connection with the preparation and filing by
the Company with the Securities Exchange Commission (the "Commission") as of the
date hereof of the registration statement on Form S-3 (the "REGISTRATION
STATEMENT") to register under the Securities Act of 1933, as amended (the
"ACT"), up to $4,000,000,000 aggregate amount of senior unsecured debt
securities (the "DEBT SECURITIES") to be issued under the indenture (the
"INDENTURE") to be entered into between the Company and Bank One Trust Company,
N.A., as trustee (the "TRUSTEE"), I have examined (i) the Company's Articles of
Incorporation and Code of Regulations, both as amended; (ii) documents issued by
public officials as to the existence of the Company under the laws of the State
of Ohio; (iii) the Registration Statement and exhibits thereto, including the
prospectus comprising a part thereof (the "PROSPECTUS") and the form of
Indenture filed as Exhibit 4(a); and (iv) such other documents and records of
the Company, and such matters of law, as I have deemed necessary to enable me to
render this opinion. I have not participated in the preparation of the
Registration Statement or the Prospectus and assume no responsibility for their
contents.

         Based on the foregoing, I am of the opinion that:

         1. The Company is a corporation duly incorporated and validly existing
in good standing under the laws of the State of Ohio.

         2. When (i) the Indenture has been duly authorized by the Board of
Directors of the Company (or by the committee to which the Board delegates the
authority to grant such authorization), and (ii) the Indenture has been validly
executed and delivered by the Company in accordance with such authorization and
by the Trustee, the Indenture will constitute a valid and legally binding
obligation of the Company enforceable against the Company in accordance with its
terms, except as may be limited by bankruptcy, insolvency, fraudulent
conveyance, reorganization, moratorium or other similar laws now or hereafter in
effect relating to or affecting the enforcement of creditors' rights generally,
general principles of equity (regardless of whether such enforceability is
considered in a proceeding in equity or at law) and an implied covenant of good
faith, fair dealing and reasonableness.

         3. When (i) the terms of the issuance and sale of the Debt Securities
have been duly approved by all necessary action of the Board of Directors of the
Company (or by the committee to which the Board delegates the authority to grant
such authorization) so as not to violate any applicable law or result in a
default under or a



breach of any agreement or instrument binding upon the Company and so as to
comply with any requirement or restriction imposed by any court or governmental
body having jurisdiction over the Company, (ii) the Indenture has been duly
executed and delivered by the Company and the Trustee thereunder and (iii) the
Debt Securities have been duly executed, authenticated, issued, delivered and
paid for as contemplated by the Registration Statement and the Prospectus and in
accordance with the Indenture, the Debt Securities will be validly issued and
will constitute valid and binding obligations of the Company enforceable against
the Company in accordance with their terms, except as may be limited by
bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium or
other similar laws now or hereafter in effect relating to or affecting the
enforcement of creditors' rights generally, general principles of equity
(regardless of whether such enforceability is considered in a proceeding in
equity or at law) and an implied covenant of good faith, fair dealing and
reasonableness.

         Paragraphs 2 and 3 of this opinion are subject to the Registration
Statement's becoming effective with no stop order with respect thereto having
been issued by the Commission, and to the issuance and continued effectiveness
of any necessary order by the Commission under the Public Utility Holding
Company Act of 1935 authorizing the issuance of the Debt Securities on the terms
contemplated in the Registration Statement and the Prospectus.

         I hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the use of my name under the caption "Legal
Opinions" in the Prospectus. In giving such consent, I do not thereby admit that
I am in the category of persons whose consent is required under Section 7 of the
Act.

         I am a member of the bar of the State of Ohio, and this opinion is
limited to the laws of the State of Ohio. Insofar as the opinion expressed
herein relates to matters which are governed by the laws of the State of New
York or the Federal laws of the United States, I have relied upon the opinion of
Pillsbury Winthrop LLP, special counsel for the Company, which is being filed as
an exhibit to the Registration Statement.

                                               Very truly yours,

                                               /s/ David L. Feltner
                                               David L. Feltner, Esq.
                                               Associate General Counsel
                                               FirstEnergy Corp.



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