"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. It was well received by music critics, who complimented its minimalist style recalling Bad Boy Records' classic hit singles of the 1990s.