
<PAGE>   1
                                                                    Exhibit 5.1 

                                Hale and Dorr
                               60 State Street
                              Boston, MA  02109
                                (617) 526-6000

 
                                         March 11, 1996

Staples, Inc.
100 Pennsylvania Avenue
P.O. Box 9328
Framingham, MA  01701-9328

Ladies and Gentlemen:

        We have assisted in the preparation of the Registration Statement on
Form S-3 (the "Registration Statement") filed with the Securities and
Exchange Commission under the Securities Act of 1933, as amended, relating to
the registration of 87,260 shares of common stock, $0.0006 par value per share
(the "Shares"), of Staples, Inc., a Delaware corporation (the "Company"), held
by certain selling stockholders of the Company.

        We have examined the Certificate of Incorporation and By-Laws of the
Company and all amendments thereto and have examined and relied on the
originals, or copies certified to our satisfaction, of such records of meetings,
written actions in lieu of meetings, or resolutions adopted at meetings, of the
directors of the Company and such other documents and instruments as in our
judgment are necessary or appropriate to enable us to render the opinions
expressed below.

        In our examination of the foregoing documents, we have assumed (i) the
genuineness of all signatures and the authenticity of all documents submitted to
us as originals, (ii) the conformity to the originals of all documents submitted
to us as certified or photostatic copies, and (iii) the authenticity of the
originals of the latter documents. 

        Based upon and subject to the foregoing, we are of the opinion that the
Shares have been duly and validly authorized and issued and are fully paid and
non-assessable.

        We hereby consent to the use of our name in the Registration Statement
and in the related Prospectus under the caption "Legal Matters" and to the
filing of this opinion as an exhibit to the Registration Statement. 

                              Very truly yours,

                              /s/ Hale and Dorr

                              HALE AND DORR

