6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

___________________

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-
16 OF THE SECURITIES EXCHANGE ACT OF 1934

For the month of September 2017

Commission File Number 001-38072

___________________

NexGen Energy Ltd.

(Translation of registrant's name into English)

Suite 3150, 1021 – West Hastings Street Vancouver, B.C., Canada  V6E 0C3

 (Address of principal executive offices)

___________________

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.)

Form 20-F £Form 40-F R

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1)  £

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7)  £

DOCUMENTS FILED AS PART OF THIS FORM 6-K

See the Exhibit Index hereto.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized, on September 8, 2017.

NEXGEN ENERGY LTD.

By:  /s/ M. Joanna Cameron               

        Name:  M. Joanna Cameron

        Title:    Vice President Legal and General Counsel

EXHIBIT INDEX

Exhibit	Description
99.1	Form 52-109F1 Certification of Interim Filings - Full Certificate - Chief Executive Officer
99.2	Form 52-109F1 Certification of Interim Filings - Full Certificate - Chief Financial Officer

EX-99.1

EXHIBIT 99.1

Form 52-109F2

Certification of Interim Filings Full Certificate

I, Leigh Curyer, the Chief Executive Officer of NexGen Energy Ltd., certify the following:

1. Review: I have reviewed the interim financial report and interim MD&A (together, the "interim filings") of NexGen Energy Ltd. (the "issuer") for the interim period ended June 30, 2017.

2. No misrepresentations: Based on my knowledge, having exercised reasonable diligence, the interim filings do not contain any untrue statement of a material fact or omit to state a material fact required to be stated or that is necessary to make a statement not misleading in light of the circumstances under which it was made, with respect to the period covered by the interim filings.

3. Fair presentation: Based on my knowledge, having exercised reasonable diligence, the interim financial report together with the other financial information included in the interim filings fairly present in all material respects the financial condition, financial performance and cash flows of the issuer, as of the date of and for the periods presented in the interim filings.

4. Responsibility: The issuer's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (DC&P) and internal control over financial reporting (ICFR), as those terms are defined in National Instrument 52-109 Certification of Disclosure in Issuers' Annual and Interim Filings, for the issuer.

5. Design: Subject to the limitations, if any, described in paragraphs 5.2 and 5.3, the issuer's other certifying officer(s) and I have, as at the end of the period covered by the interim filings

(a) designed DC&P, or caused it to be designed under our supervision, to provide reasonable assurance that

(i) material information relating to the issuer is made known to us by others, particularly during the period in which the interim filings are being prepared; and

(ii) information required to be disclosed by the issuer in its annual filings, interim filings or other reports filed or submitted by it under securities legislation is recorded, processed, summarized and reported within the time periods specified in securities legislation; and

(b) designed ICFR, or caused it to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with the issuer's GAAP.

5.1 Control framework: The control framework the issuer's other certifying officer(s) and I used to design the issuer's ICFR is the Internal Control – Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

5.2N/A

5.3N/A

6. Reporting changes in ICFR: The issuer has disclosed in its interim MD&A any change in the issuer's ICFR that occurred during the period beginning on April 1, 2017 and ended on June 30, 2017 that has materially affected, or is reasonably likely to materially affect, the issuer's ICFR.

Date: August 10, 2017

"Leigh Curyer"                         

Leigh Curyer

Chief Executive Officer

EX-99.2

EXHIBIT 99.2

Form 52-109F2

Certification of Interim Filings Full Certificate

I, Grace Marosits, the Chief Financial Officer of NexGen Energy Ltd., certify the following:

1. Review: I have reviewed the interim financial report and interim MD&A (together, the "interim filings") of NexGen Energy Ltd. (the "issuer") for the interim period ended June 30, 2017.

2. No misrepresentations: Based on my knowledge, having exercised reasonable diligence, the interim filings do not contain any untrue statement of a material fact or omit to state a material fact required to be stated or that is necessary to make a statement not misleading in light of the circumstances under which it was made, with respect to the period covered by the interim filings.

3. Fair presentation: Based on my knowledge, having exercised reasonable diligence, the interim financial report together with the other financial information included in the interim filings fairly present in all material respects the financial condition, financial performance and cash flows of the issuer, as of the date of and for the periods presented in the interim filings.

4. Responsibility: The issuer's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (DC&P) and internal control over financial reporting (ICFR), as those terms are defined in National Instrument 52-109 Certification of Disclosure in Issuers' Annual and Interim Filings, for the issuer.

5. Design: Subject to the limitations, if any, described in paragraphs 5.2 and 5.3, the issuer's other certifying officer(s) and I have, as at the end of the period covered by the interim filings

(a) designed DC&P, or caused it to be designed under our supervision, to provide reasonable assurance that

(i) material information relating to the issuer is made known to us by others, particularly during the period in which the interim filings are being prepared; and

(ii) information required to be disclosed by the issuer in its annual filings, interim filings or other reports filed or submitted by it under securities legislation is recorded, processed, summarized and reported within the time periods specified in securities legislation; and

(b) designed ICFR, or caused it to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with the issuer's GAAP.

5.1 Control framework: The control framework the issuer's other certifying officer(s) and I used to design the issuer's ICFR is the Internal Control – Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

5.2 N/A

5.3 N/A

6. Reporting changes in ICFR: The issuer has disclosed in its interim MD&A any change in the issuer's ICFR that occurred during the period beginning on April 1, 2017 and ended on June 30, 2017 that has materially affected, or is reasonably likely to materially affect, the issuer's ICFR.

Date: August 10, 2017

"Grace Marosits"             

Grace Marosits

Chief Financial Officer