"Must Be Love" is a song recorded by American singer Cassie. It features guest vocals by American rapper Puff Daddy, who also co-wrote the song with Aion Clarke, Michael Jones, Leroy Watson and the producer Mario Winans. The song was released for digital download in the United States on April 14, 2009, by Atlantic Records under the Bad Boy imprint, impacting urban radio stations in that region on April 27, 2009.

Casandra Elizabeth Ventura, known mononymously as Cassie, is an American singer, dancer, actress, and model. Born in New London, Connecticut, she began her musical career after meeting record producer Ryan Leslie in late 2004, who signed her to his record label, NextSelection Lifestyle Group. Two years later, Ventura released her debut single "Me & U", which was discovered by rapper Sean "Diddy" Combs; Leslie agreed to partner his NextSelection imprint with Combs' Bad Boy Records for the commercial release of her debut album. The song marked the first of her two entries on the Billboard Hot 100, peaking at number three by July 2006.