<Page>


                                                                     Exhibit 5.1


FOLEY HOAG
ATTORNEYS AT LAW

August 17, 2001

The J. Jill Group, Inc.
4 Batterymarch Park
Quincy, Massachusetts 02169

       Re:  The J. Jill Group, Inc.
            2001 Incentive and Non-Statutory Stock Option Plan

Ladies and Gentlemen:

       We are familiar with the Registration Statement on Form S-8 (the
"Registration Statement") to be filed by The J. Jill Group, Inc., a Delaware
corporation (the "Company"), with the Securities and Exchange Commission (the
"Commission") under the Securities Act of 1933, as amended (the "Securities
Act"), relating to the offering by the Company of up to 1,000,000 shares (the
"Shares") of its common stock, par value $0.01 per share, issuable upon exercise
of stock options granted or to be granted pursuant to The J. Jill Group, Inc.
2001 Incentive and Non-Statutory Stock Option Plan (the "Plan").

       In arriving at the opinion expressed below, we have examined and relied
on the Restated Certificate of Incorporation of the Company, as amended to date,
the By-Laws of the Company, as amended to date, the records of meetings and
consents of the Board of Directors and stockholders of the Company provided to
us by the Company relating to the Plan and the Shares, the Registration
Statement and the Plan.

       In addition, we have examined and relied on the originals or copies
certified or otherwise identified to our satisfaction of all such corporate
records of the Company and such other instruments and other certificates of
public officials, officers and representatives of the Company and such other
persons, and we have made such examination of law, as we have deemed appropriate
as a basis for the opinion expressed below.

       We assume that all Shares to be issued upon exercise of options granted
or to be granted pursuant to the Plan will be issued in accordance with the
terms of the Plan and that the purchase price of the Shares, or the value of
other consideration received or to be received by the Company for the Shares,
will be greater than or equal to the par value per share of the Shares.

       Based upon and subject to the foregoing, it is our opinion that the
Shares, when issued and delivered upon the exercise of options and against the
receipt of the purchase price or other consideration therefor, will be validly
issued, fully paid and nonassessable.

       This opinion is to be used only in connection with the offer and sale of
the Shares while the Registration Statement is in effect.




The J. Jill Group, Inc.
August 17, 2001
Page 2

       Please note that we are opining only as to the matters expressly set
forth herein, and no opinion should be inferred as to any other matters.

       We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement in accordance with the requirements of Item 601(b)(5) of
Regulation S-K under the Securities Act and to the reference to our firm under
the caption, "Interests of Named Experts and Counsel."

                                         FOLEY HOAG & ELIOT LLP



                                         By: /s/ DAVID R. PIERSON
                                            ------------------------------------
                                            A Partner