"Knock You Down" is a song by American singer and songwriter Keri Hilson, recorded for her debut album, In a Perfect World. . . . The song features guest vocals from Ne-Yo and Kanye West. All three artists co-wrote the song with its producer Nate "Danja" Hills, as well as Kevin Cossom and Marcella Araica. The song was released first released to rhythmic and urban airplay in the United States as the album's fourth single in the US, and it would later serve as the third worldwide single.