NASDAQ OMX Group (NDAQ)

SKADDEN, ARPS, SLATE, MEAGHER & FLOM LLP

Four Times Square

New York, New York 10036-6522

November 8, 2007

The Nasdaq Stock Market, Inc.

One Liberty Plaza

New York, NY 10006

Ladies and Gentlemen:

We have acted as special counsel to The Nasdaq Stock Market, Inc., a Delaware corporation (the “Company”), in connection with the Registration Statement on Form S-3 (the “Registration Statement”), filed on January 30, 2006, by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”), allowing for delayed offerings pursuant to Rule 415 under the Act. The Registration Statement includes a prospectus as supplemented by a prospectus supplement (the “Prospectus”) relating to the offering by Hellman & Friedman Capital Partners IV, L.P., H&F Executive Fund IV, L.P., H&F International Partners IV-A, L.P., H&F International Partners IV-B, L.P., Silver Lake Partners TSA, L.P., Silver Lake Investors, L.P., Silver Lake Partners II TSA, L.P., Silver Lake Technology Investors II, L.P, Integral Capital Partners VI, L.P. and VAB Investors, LLC (the “Selling Stockholders”) of an aggregate of up to 36,152,136 shares of the Company’s common stock (“Common Stock”), par value $.01 per share (the “Secondary Shares”). The Secondary Shares consist of up to 35,652,136, shares of Common Stock to be issued upon conversion of the Company’s 3.75% Convertible Notes due 2012 (the “Notes”) issued pursuant to the Indenture dated as of April 22, 2005, between the Company and Law Debenture Trust Company of New York (the “Indenture”) as supplemented by the First Supplemental Indenture, dated December 8, 2005 between the Company and Law Debenture Trust Company of New York (the “First Supplemental Indenture”) and the Second Supplemental Indenture, dated as of November 9, 2006 among the Company, The Nasdaq Stock Market, LLC and Law Debenture Trust Company of New York (the “Second Supplemental Indenture”) and exercise of the Company’s Series A Warrants and Series B Warrants (the “Warrants” and the “New Secondary Shares,”

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respectively) and 500,000 shares of Common Stock held by certain of the Selling Stockholders (the “Existing Secondary Shares”).

This opinion is being furnished in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Act.

In rendering the opinions set forth herein, we have examined and relied on originals or copies of:

(i) the Registration Statement;

(ii) the Prospectus;

(iii) the Restated Certificate of Incorporation of the Company, as amended to the date hereof and as certified by the Secretary of State of the State of Delaware;

(iv) the By-laws of the Company, as currently in effect and as certified by the Secretary of the Company;

(v) certain resolutions of the Board of Directors of the Company relating to the issuance of the Secondary Shares and related matters;

(vi) stock certificate representing the Existing Secondary Shares;

(vii) the Indenture;

(viii) the First Supplemental Indenture;

(ix) the Second Supplemental Indenture;

(x) the Warrants;

(xi) the Notes; and

(xii) a specimen common stock certificate representing the Common Stock.

We also have examined originals or copies, certified or otherwise identified to our satisfaction, of such records of the Company and such agreements, certificates and receipts of public officials, certificates of officers or other representatives of the Company and others, and such other documents as we have deemed necessary or appropriate as a basis for the opinions set forth herein.

In our examination, we have assumed the legal capacity of all natural persons, the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as facsimile, electronic, certified or photostatic copies, and the authenticity of the originals of such copies. In making our examination of executed documents, we have assumed that the parties thereto, other than the Company, had the power, corporate or other, to enter into and perform all obligations thereunder

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November 8, 2007

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and have also assumed the due authorization by all requisite action, corporate or other, and the execution and delivery by such parties of such documents and the validity and binding effect thereof on such parties. In rendering the opinion set forth below, we have assumed that the Company has received the entire amount of the consideration contemplated by the resolutions of the Board of Directors of the Company authorizing the issuance of the Secondary Shares and that the stock certificates evidencing the New Secondary Shares will conform to the specimen stock certificate examined by us and will be duly executed and delivered. As to any facts material to the opinions expressed herein that we did not independently establish or verify, we have relied upon statements and representations of officers and other representatives of the Company and others and of public officials.

The Secondary Shares may be offered and sold by the Selling Stockholders from time to time on a delayed or continuous basis, and this opinion is limited to the laws as in effect on the date hereof, which laws are subject to change with possible retroactive effect.

Based upon and subject to the foregoing and to the other qualifications and limitations set forth herein, we are of the opinion that (i) the Existing Secondary Shares have been duly authorized and validly issued, and are fully paid and nonassessable and (ii) the New Secondary Shares have been duly authorized, and when issued and delivered upon conversion of the Notes or the exercise of the Warrants, as applicable, will be validly issued, fully paid and nonassessable.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement. We also consent to the reference to our firm under the caption “Legal Matters” in the Prospectus. In giving this consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission. This opinion is expressed as of the date hereof unless otherwise expressly stated, and we disclaim any undertaking to advise you of any subsequent changes in the facts stated or assumed herein or of any subsequent changes in applicable laws.

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SKADDEN, ARPS, SLATE, MEAGHER & FLOM LLP

Four Times Square

New York, New York 10036-6522

May 11, 2006

The Nasdaq Stock Market, Inc.

One Liberty Plaza

New York, NY 10006

Ladies and Gentlemen:

We have acted as special counsel to The Nasdaq Stock Market, Inc., a Delaware corporation (the “Company”), in connection with the Registration Statement on Form S-3 (File No. 333-131373) (the “Registration Statement”), filed on January 30, 2006 by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”) and any prospectus supplements, as amended or supplemented filed by the Company with the Commission under Rule 424(b) of the Act relating to the sale, from time to time, of up to 14,201,625 shares (the “Offered Shares”) of common stock, $0.01 par value per share, of the Company ( “Common Stock”) by certain selling stockholders of the Company.

This opinion is being delivered in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Act.

In connection with this opinion, we have examined originals or copies, certified or otherwise identified to our satisfaction, of:

(b) the Amended and Restated Certificate of Incorporation of the Company, as amended to the date hereof and as certified by the Secretary of State of the State of Delaware (the “Certificate of Incorporation”);

(c) the Amended and Restated Bylaws of the Company, as currently in effect and as certified by the Secretary of the Company (the “Bylaws”);

We have also examined originals or copies, certified or otherwise identified to our satisfaction, of such records of the Company and such agreements, certificates of public officials, certificates

of officers or other representatives of the Company and others, and such other documents, certificates and records as we have deemed necessary or appropriate as a basis for the opinion set forth herein.

In our examination, we have assumed the legal capacity of all natural persons, the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as electronic, certified, conformed, photostatic or facsimile copies and the authenticity of the originals of such latter documents. In making our examination of executed documents or documents to be executed, we have assumed that the parties thereto, other than the Company, had or will have the power, corporate or other, to enter into and perform all obligations thereunder. As to any facts material to the opinion expressed herein which were not independently established or verified, we have relied upon oral or written statements and representations of officers and other representatives of the Company and others.

In rendering the opinion set forth below, we have relied solely on the stock record books of the Company in determining the number of issued and outstanding shares of capital stock of the Company and have assumed that the consideration recited in the resolutions of the Board of Directors, the Audit Committee and the Finance Committee (or any committee thereof) of the Company approving the issuance of all such shares has been received in full by the Company (other than such shares of the Common Stock that were issued as a stock dividend, for which no consideration was required). We have assumed that the certificates representing the Offered Shares have been manually signed by an authorized officer of the transfer agent and registrar for the Common Stock and conform to the specimen certificate examined by us evidencing the Common Stock.

Our opinion set forth herein is limited to Delaware corporate law and the laws of the State of New York that, in our experience, are normally applicable to transactions of the type contemplated by the Registration Statement and any prospectus supplement and, to the extent that judicial or regulatory orders or decrees or consents, approvals, licenses, authorizations, validations, filings, recordings or registrations with governmental authorities are relevant, to those required under such laws (all of the foregoing being referred to as “Opined on Law”). We do not express any opinion with respect to the law of any jurisdiction other than Opined on Law or as to the effect of any such non-opined law on the opinion herein stated. The Offered Securities may be issued from time to time on a delayed or continuous basis, and this opinion is limited to the laws, including the rules and regulations, as in effect on the date hereof, which laws are subject to change with possible retroactive effect.

Based upon and subject to the foregoing and the limitations, qualifications, exceptions and assumptions set forth herein, we are of the opinion that the Offered Shares being sold by the selling stockholders have been duly authorized, validly issued, fully paid and nonassessable.

We hereby consent to the filing of this opinion with the Commission as an exhibit to a Current Report on Form 8-K and its incorporation by reference into the Registration Statement. We also hereby consent to the use of our name under the heading “Legal Matters” in a prospectus supplement. In giving this consent, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission promulgated thereunder. This opinion is expressed as of the date hereof unless

otherwise expressly stated, and we disclaim any undertaking to advise you of any subsequent changes in the facts stated or assumed herein or of any subsequent changes in applicable laws.

Very truly yours,

/s/ Skadden, Arps, Slate, Meagher & Flom LLP