Prescott Group Capital Management Raises Exposure to Enova International, Inc. (ENVA)

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13D

(Rule 13d-101)

Under the Securities Exchange Act of 1934

Enova
International, Inc.

(Name of Issuer)

Common Stock, $.00001 par value per share

(Title of Class of Securities)

29357K103

(CUSIP NUMBER)

Phil Frohlich

1924 South Utica, Suite #1120

Tulsa, Oklahoma 74104-6429

(918) 747-3412

(Name,
Address and Telephone Number of Person Authorized to Receive Notices and Communications)

– with copies to –

Eliot D. Raffkind

Akin,
Gump, Strauss, Hauer & Feld, L.L.P.

1700 Pacific Avenue, Suite 4100

Dallas, Texas 75201-4618

(214) 969-2800

March 15, 2016

(Date of event which requires filing of this statement)

If the filing person has
previously filed a statement on Schedule 13G to report the acquisition which is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g) check the following box  ¨.

The information required in the remainder of this cover page shall not be deemed to be filed for
the purpose of Section 18 of the Securities Exchange Act of 1934, as amended (the Act), or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act.

Page 2 of 13

Page 3 of 13

Page 4 of 13

Page 5 of 13

SCHEDULE 13D

This Schedule 13D (this Schedule 13D) is being filed on behalf of Prescott Group Capital Management, L.L.C., an Oklahoma limited
liability company (Prescott Capital), Prescott Group Aggressive Small Cap, L.P., an Oklahoma limited partnership (Prescott Small Cap), Prescott Group Aggressive Small Cap II, L.P., an Oklahoma limited partnership
(Prescott Small Cap II and, together with Prescott Small Cap, the Small Cap Funds) and Mr. Phil Frohlich, the principal of Prescott Capital, relating to shares of common stock of Enova International, Inc., a Delaware
corporation (the Issuer).

This Schedule 13D relates to shares of Common Stock, $.00001 par value per share, of the Issuer
(the Common Stock) purchased by the Small Cap Funds through the account of Prescott Group Aggressive Small Cap Master Fund, G.P., an Oklahoma general partnership (Prescott Master Fund), of which the Small Cap Funds are the
general partners. Prescott Capital serves as the general partner of the Small Cap Funds and may direct the Small Cap Funds, the general partners of Prescott Master Fund, to direct the vote and disposition of the 1,909,457 shares of Common Stock held
by the Prescott Master Fund. As the principal of Prescott Capital, Mr. Frohlich may direct the vote and disposition of the 1,909,457 shares of Common Stock held by Prescott Master Fund.

Securities acquired: Common Stock, $.00001 par value
per share (the Common Stock).

(a) This Schedule 13D is jointly filed by Prescott
Capital, Prescott Small Cap, Prescott Small Cap II and Phil Frohlich. Because Phil Frohlich is the managing member of Prescott Capital, which is the general partner of the Small Cap Funds (with Phil Frohlich and Prescott Capital hereinafter referred
to as the Controlling Persons), the Controlling Persons may be deemed, pursuant to Rule 13d-3 of the Securities Exchange Act of 1934, as amended (the Act), to be the beneficial owners of all of the shares of Common Stock held
by the Small Cap Funds. The Reporting Persons (as hereinafter defined) are filing this Schedule 13D jointly, as they may be considered a group under Section 13(d)(3) of the Act. However, neither the fact of this filing nor anything
contained herein shall be deemed to be an admission by the Reporting Persons that such a group exists.

(b) The principal place of business
for each of the Reporting Persons is 1924 South Utica, Suite #1120, Tulsa, Oklahoma, 74104.

Page 6 of 13

(c) The principal occupation of Phil Frohlich is serving as the managing member of Prescott
Capital. The principal business of Prescott Capital is acting as the general partner of the Small Cap Funds. The principal business of the Small Cap Funds is investing in securities.

(d) During the last five years, none of the Reporting Persons have been convicted in a criminal proceeding (excluding traffic violations or
similar misdemeanors).

(e) During the last five years, none of the Reporting Persons have been a party to a civil proceeding of a judicial
or administrative body of competent jurisdiction and as a result of such proceeding were or are subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state
securities laws or finding any violation with respect to such laws.

(f) Prescott Capital and the Small Cap Funds are organized under the
laws of the State of Oklahoma. Mr. Frohlich is a citizen of the United States of America.

As of March 15, 2016, the Small Cap Funds had
invested $19,732,058 (inclusive of brokerage commissions) in shares of Common Stock of the Issuer. The source of these funds was the working capital of the Small Cap Funds.

The Small Cap Funds (together with Phil Frohlich and
Prescott Capital, the Reporting Persons) purchased the Common Stock based on the belief that such securities, when purchased, were undervalued and represented an attractive investment opportunity. Although the Reporting Persons have no
specific plan or proposal to acquire or dispose of the Common Stock, consistent with their investment purpose, the Reporting Persons at any time and from time to time may acquire additional Common Stock or dispose of any or all of their Common Stock
depending upon an ongoing evaluation of the investment in the Common Stock, prevailing market conditions, other investment opportunities, liquidity requirements of the Reporting Persons and/or other investment considerations.

The purpose of the acquisition of the Common Stock was for investment, and the acquisitions of the Common Stock were made in the ordinary
course of business and were not made for the purpose of acquiring control of the Issuer.

Also, consistent with the investment purpose,
the Reporting Persons may engage in communications with one or more shareholders of the Issuer, one or more officers of the Issuer and/or one or more members of the board of directors of the Issuer and/or one or more representatives or regulators of
the Issuer regarding the Issuer, including, but not limited to, its operations. The Reporting Persons may discuss ideas that, if effected, may result in any of the following: the acquisition by persons of additional Common Stock of the Issuer, an
extraordinary corporate transaction involving the Issuer and/or changes in the board of directors or management of the Issuer.

Page 7 of 13

Except to the extent the foregoing may be deemed a plan or proposal, the Reporting Persons have
no plans or proposals which relate to, or could result in, any of the matters referred to in paragraphs (a) through (j), inclusive, of the instructions to Item 4 of the Schedule 13D. The Reporting Persons may, at any time and from time to
time, review or reconsider their position and/or change their purpose and/or formulate plans or proposals with respect thereto.

(a) The aggregate percentage of shares of
Common Stock reported to be owned by the Reporting Persons is based upon 33,152,974 shares outstanding, which is the total number of shares of Common Stock outstanding as of March 3, 2016 pursuant to the Issuers Form 10-K filed with the
Securities and Exchange Commission on March 7, 2016.

As of March 15, 2016, the Small Cap Funds beneficially owned 1,909,457
shares of Common Stock, representing approximately 5.8% of the issued and outstanding Common Stock of the Issuer.

Prescott Capital, as
the general partner of the Small Cap Funds, may also be deemed to beneficially own the 1,909,457 shares of Common Stock held by the Small Cap Funds, representing approximately 5.8% of the issued and outstanding Common Stock of the Issuer.

In addition, Phil Frohlich, as managing member of Prescott Capital, the general partner of the Small Cap Funds, may also be deemed to
beneficially own the 1,909,457 shares of Common Stock beneficially owned by the Small Cap Funds, representing approximately 5.8% of the issued and outstanding Common Stock of the Issuer.

Prescott Capital and Mr. Frohlich disclaim beneficial ownership of the shares of Common Stock held by the Small Cap Funds except to the
extent of their pecuniary interest therein.

(b) By virtue of his position with Prescott Capital and the Small Cap Funds, Phil Frohlich
has the sole power to vote and dispose of the shares of Common Stock owned by the Small Cap Funds reported in this Schedule 13D.

The
filing of this statement on Schedule 13D shall not be construed as admission that Prescott Capital or Mr. Frohlich is for the purposes of Section 13(d) or 13(g) of the Securities Exchange Act of 1934, as amended, the beneficial owner of
any of the 1,909,457 shares of Common Stock owned by the Small Cap Funds. Pursuant to Rule 13d-4, Prescott Capital and Mr. Frohlich disclaim all such beneficial ownership.

(c) Annex A attached hereto lists all transactions in the Common Stock during the past sixty (60) days by the Reporting Persons. The
transactions in the Common Stock were effected in the open market.

Page 8 of 13

(d) No person other than the Reporting Persons is known to have the right to receive, or the
power to direct the receipt of dividends from, or proceeds from the sale of, the shares of Common Stock.

(e) Not applicable.

Other than as described herein, there are no contracts, arrangements, understandings or relationships among the Reporting Persons, or between
the Reporting Persons and any other person, with respect to the securities of the Issuer.

Page 9 of 13

Signatures

After reasonable inquiry and to the best of their knowledge and belief, each of the undersigned certifies that the information set forth in
this statement is true, complete and correct.

Dated: March 16, 2016

Page 10 of 13