"Day 'n' Nite" is the debut single by American rapper Kid Cudi. The song was written and produced by Cudi alongside his longtime collaborator and friend, Brooklyn-based producer Dot da Genius. It was issued as Cudi's commercial debut single on February 5, 2008, but had initially been released on Cudi's MySpace page and later featured on several music blogs in November 2007.

Scott Ramon Seguro Mescudi, also known by his stage name Kid Cudi, is an American rapper, singer, songwriter, record producer, actor, and fashion designer. Born and raised in Cleveland, Cudi moved to New York City in pursuit of a musical career, where he first gained recognition for his song "Day 'n' Nite." Initially self-published on his MySpace page, the song became a hit online and served as a catalyst for Cudi to team up with record producers Plain Pat and Emile Haynie to record his first full-length project, a mixtape titled A Kid Named Cudi (2008). Its release helped Cudi rise to prominence and establish a fanbase, catching the attention of rapper Kanye West—who signed Cudi to his GOOD Music label by late 2008.