UNITED STATES SECURITIES AND EXCHANGE COMMISSION For the quarterly period ended September 30, 2020 OR ¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission File Number: 814-00646 APOLLO INVESTMENT CORPORATION FORM 10-Q Washington, D.C. 20549 x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smal ...