Man on the Moon: The End of Day is the debut studio album by the American rapper Kid Cudi. It was released on September 15, 2009, through Dream On, GOOD Music, and Universal Motown Records. A concept album narrated by fellow rapper and GOOD Music labelmate Common, it follows the release of his first full-length project A Kid Named Cudi (2008), and is the first installment of the Man on the Moon trilogy. Production was handled by several high-profile record producers, including Kanye West, Emile Haynie, Plain Pat, and Jeff Bhasker, as well as contributions from Dot da Genius, Free School and the Kickdrums, among others.

Man on the Moon: The End of Day spawned three singles—"Day 'n' Nite", "Make Her Say" and "Pursuit of Happiness"—that attained chart success and multiplatinum to diamond-certifications by the Recording Industry Association of America (RIAA). To further promote the album, he toured with Asher Roth and Lady Gaga, respectively. Man on the Moon: The End of Day also received three Grammy Awards nominations.