Exhibit 5.1

July 24, 2018

Liquidia Technologies, Inc.

419 Davis Drive, Suite 100

Morrisville, North Carolina 27560

Re:                             Registration Statement on Form S-1 (Registration No. 333-225960)

Ladies and Gentlemen:

We have acted as counsel to Liquidia Technologies, Inc., a Delaware corporation (the “Company”), in connection with the referenced Registration Statement on Form S-1 (as amended and supplemented from time to time, the “Registration Statement”) initially filed by the Company on June 28, 2018 with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”).  The Registration Statement relates to the offer and sale by the Company of up to an aggregate of 5,227,273 shares of the Company’s common stock, par value $0.001 per share, through the consummation of an initial public offering (all such shares, together with any additional shares of such stock that may be issued by the Company pursuant to Rule 462(b) (as prescribed by the Commission pursuant to the Securities Act), the “Shares”). We understand that the Shares are to be sold to the underwriters for resale to the public as described in the Registration Statement and pursuant to an underwriting agreement, substantially in the form filed as an exhibit to the Registration Statement, to be entered into by and among the Company and the representatives of the underwriters (the “Underwriting Agreement”).

As the basis for the opinions hereinafter expressed, we have examined: (i) originals, or copies certified or otherwise identified, of (a) the Registration Statement; (b) certain resolutions of the Board of Directors of the Company; (c) the form of amended and restated certificate of incorporation of the Company (in the form filed as Exhibit 3.4 to the Registration Statement) (the “Certificate of Incorporation”), and the form of amended and restated bylaws of the Company (in the form filed as Exhibit 3.6 of the Registration Statement); and (d) such other records, agreements, other instruments and documents as we have deemed necessary or advisable for the purposes of this opinion; and (ii) such statutes, including the Delaware General Corporation Law, and regulations as we have deemed necessary or advisable for the purposes of this opinion. We have not independently verified any factual matter relating to this opinion. As to questions of fact material to this opinion, we have relied upon certificates or comparable documents of public officials and of officers and representatives of the Company.

In our examination of the foregoing documents, we have assumed 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 copies, the authenticity of the originals of such latter documents and the legal competence of all signatories to such documents.

We express no opinion other than as to the federal laws of the United States of America and the Delaware General Corporation Law (including the statutory provisions, the applicable provisions of the Delaware Constitution and reported judicial decisions interpreting the foregoing).

Based upon the foregoing, and subject to the qualifications, assumptions and limitations stated herein, we are of the opinion that upon payment and delivery of the Shares at the price per share approved by the Pricing Committee of the Board of Directors of the Company, the Shares will be validly issued, fully paid and nonassessable.

In addition to the qualifications set forth above, the foregoing opinion is further qualified as follows:

(a)         The foregoing opinion is rendered as of the date hereof. We assume no obligation to update such opinion to reflect any facts or circumstances that may hereafter come to our attention or changes in the law which may hereafter occur.

(b)         This opinion is limited to the matters set forth herein, and no other opinion should be inferred beyond the matters expressly stated.

We hereby consent to the use of this opinion as an exhibit to the Registration Statement, and we consent to the reference to this firm under the caption “Legal Matters” in the prospectus forming part of the Registration Statement. The giving of this consent, however, does not constitute an admission that we are “experts” within the meaning of Section 11 of the Securities Act or within the category of persons whose consent is required by Section 7 of the Securities Act.

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