GIBSON DUNN

Exhibit 5.1

Gibson, Dunn & Crutcher LLP

200 Park Avenue

New York, NY 10166-0193

Tel 212.351.4000

www.gibsondunn.com

C 42498-00008

November 10, 2016

Hewlett Packard Enterprise Company

3000 Hanover Street

Palo Alto, California 94304

(650) 857-1501

Re:Hewlett Packard Enterprise Company Registration Statement on Form S-4

Ladies and Gentlemen:

We have acted as counsel to Hewlett Packard Enterprise Company, a Delaware corporation (the “Company”) in connection with the preparation and filing with the Securities and Exchange Commission (the “Commission”) of a Registration Statement on Form S-4 (the “Registration Statement”), under the Securities Act of 1933, as amended (the “Securities Act”), in connection with the offering by the Company of up to (i) $2,250,000,000 2.450% Notes due 2017, (ii) $2,650,000,000 2.850% Notes due 2018, (iii) $3,000,000,000 3.600% Notes due 2020, (iv) $1,350,000,000 4.400% Notes due 2022, (v) $2,500,000,000 4.900% Notes due 2025, (vi) $750,000,000 6.200% Notes due 2035, (vii) $1,500,000,000 6.350% Notes due 2045, (viii) $350,000,000 Floating Rate Notes due 2017 and (ix) $250,000,000 Floating Rate Notes due 2018 (together, the “New Notes”), in exchange for a like principal amount of the Company’s outstanding (i) $2,250,000,000 2.450% Notes due 2017, (ii) $2,650,000,000 2.850% Notes due 2018, (iii) $3,000,000,000 3.600% Notes due 2020, (iv) $1,350,000,000 4.400% Notes due 2022, (v) $2,500,000,000 4.900% Notes due 2025, (vi) $750,000,000 6.200% Notes due 2035, (vii) $1,500,000,000 6.350% Notes due 2045, (viii) $350,000,000 Floating Rate Notes due 2017 and (ix) $250,000,000 Floating Rate Notes due 2018 (together, the “Outstanding Notes”).

The Outstanding Notes have been issued pursuant to the Indenture dated as of October 9, 2015(the “Base Indenture”), between the Company and The Bank of New York Mellon Trust Company, N.A.,

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GIBSON DUNN

as trustee (the “Trustee”), as supplemented by (i) First Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the 2.450% Notes due 2017 (the “First Supplemental Indenture”), (ii) Second Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the 2.850% Notes due 2018 (the “Second Supplemental Indenture”), (iii) Third Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the 3.600% Notes due 2020 (the “Third Supplemental Indenture”), (iv) Fourth Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the 4.400% Notes due 2022 (the “Fourth Supplemental Indenture”), (v) Fifth Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the 4.900% Notes due 2025 (the “Fifth Supplemental Indenture”), (vi) Sixth Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the 6.200% Notes due 2035 (the “Sixth Supplemental Indenture”), (vii) Seventh Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the 6.350% Notes due 2045 (the “Seventh Supplemental Indenture”), (viii) Eighth Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the Floating Rate Notes due 2017 (the “Eighth Supplemental Indenture”) and (ix) Ninth Supplemental Indenture, dated as of October 9, 2015, between the Company and the Trustee, with respect to the Floating Rate Notes due 2018 (the “Ninth Supplemental Indenture” and together with the Base Indenture, the First Supplemental Indenture, the Second Supplemental Indenture, the Third Supplemental Indenture, the Fourth Supplemental Indenture, the Fifth Supplemental Indenture, the Sixth Supplemental Indenture, the Seventh Supplemental Indenture and the Eighth Supplemental Indenture, the “Indenture”).

In arriving at the opinions expressed below, we have examined originals, or copies certified or otherwise identified to our satisfaction as being true and complete copies of the originals, of the Base Indenture, the First Supplemental Indenture, the Second Supplemental Indenture, the Third Supplemental Indenture, the Fourth Supplemental Indenture, the Fifth Supplemental Indenture, the Sixth Supplemental Indenture, the Seventh Supplemental Indenture, the Eighth Supplemental Indenture, the Ninth Supplemental Indenture, the Outstanding Notes, the New Notes and such other documents, corporate records, certificates of officers of the Company and of public officials and other instruments as we have deemed necessary or advisable to enable us to render these opinions. In our examination, we have assumed, without independent investigation, the genuineness of all signatures, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals and the conformity to original documents of all documents submitted to us as copies. As to any facts material to this opinion, we have relied to the extent we deemed appropriate and without independent investigation upon statements and representations of officers and other representatives of the Company and others.

Based upon the foregoing, and subject to the assumptions, exceptions, qualifications and limitations set forth herein, we are of the opinion that when the New Notes are executed and authenticated in accordance with the provisions of the Indenture and issued and delivered in exchange for the Outstanding Notes in the manner described in the Registration Statement, the New Notes will constitute legal, valid and binding obligations of the Company.

GIBSON DUNN

The opinion expressed above is subject to the following additional exceptions, qualifications, limitations and assumptions:

A.We render no opinion herein as to matters involving the laws of any jurisdiction other than the State of New York. This opinion is limited to the effect of the current state of the laws of the State of New York and the facts as they currently exist. We assume no obligation to revise or supplement this opinion in the event of future changes in such laws or the interpretations thereof or such facts.

B.The opinion above is subject to (i) the effect of any bankruptcy, insolvency, reorganization, moratorium, arrangement or similar laws affecting the rights and remedies of creditors’ generally, including without limitation the effect of statutory or other laws regarding fraudulent transfers or preferential transfers, and (ii) general principles of equity, including without limitation concepts of materiality, reasonableness, good faith and fair dealing and the possible unavailability of specific performance, injunctive relief or other equitable remedies regardless of whether enforceability is considered in a proceeding in equity or at law.

C.We express no opinion regarding the effectiveness of (i) any waiver of stay, extension or usury laws or of unknown future rights, (ii) provisions relating to indemnification, exculpation or contribution, to the extent such provisions may be held unenforceable as contrary to public policy or federal or state securities laws, (iii) any provision waiving the right to object to venue in any court, (iv) any agreement to submit to the jurisdiction of any Federal court, or (v) any waiver of the right to jury trial.

We consent to the filing of this opinion as an exhibit to the Registration Statement, and we further consent to the use of our name under the caption “Legal Matters” in the Registration Statement and the prospectus that forms a part thereof. In giving these consents, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/ Gibson, Dunn & Crutcher LLP