"Knock You Down" is a song by American singer-songwriter Keri Hilson, taken from her debut studio album, In a Perfect World... (2009). The song features guest vocals from American singer-songwriter Ne-Yo and American rapper Kanye West. The song was written by Hilson, West, and Ne-Yo along with Kevin Cossom and Marcella Araica. Danja, who produced the track, also receives writing credits. The song is an electrohop and R&B number, which includes elements of pop music. 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. The lyrics of the song pertain to how love "knocks you down." Part of the song refers to Michael Jackson; coincidentally it was released at the time surrounding the death of the late singer. The song received generally positive to mixed reviews, with critics divided as to whether Ne-Yo and West overwhelmed Hilson's appearance. However, reviewers also complimented that the song was radio-friendly. It was nominated for multiple awards, including Best Rap/Sung Collaboration at the 52nd Grammy Awards.

Kanye Omari West ( /ˈkɑːnjeɪ/; born June 8, 1977) is an American musician, film director and fashion designer. West first rose to fame as a producer for Roc-A-Fella Records, where he eventually achieved recognition for his work on Jay-Z's album The Blueprint, as well as hit singles for musical artists including Alicia Keys, Ludacris, and Janet Jackson. His style of production originally used pitched-up vocal samples from soul songs incorporated with his own drums and instruments. However, subsequent productions saw him broadening his musical palette and expressing influences encompassing '70s R&B, baroque pop, trip hop, arena rock, folk, alternative, electronica, synthpop, and classical music.

West released his debut album The College Dropout in 2004, his second album Late Registration in 2005, his third album Graduation in 2007, his fourth album 808s & Heartbreak in 2008, and his fifth album My Beautiful Dark Twisted Fantasy in 2010. West released a collaborative album, Watch the Throne with Jay-Z in 2011, which is the duo's first collaborative album. His five solo albums, all of which have gone platinum, have received numerous awards and critical acclaim. As of 2012, West has won a total of eighteen Grammy Awards, making him one of the most awarded artists of all-time. All albums have been very commercially successful, with My Beautiful Dark Twisted Fantasy becoming his fourth consecutive No. 1 album in the U.S. upon release. West has had 5 songs exceed 3 million in digital sales as of July 2011, with "Gold Digger" selling 3,086,000, "Stronger" selling 4,402,000, "Heartless" selling 3,742,000, "E.T." selling over 4,000,000 and "Love Lockdown" selling over 3,000,000 placing him third in overall digital sales of the past decade. He has sold over 30 million digital songs in the United States making him one of the best-selling digital artists of all-time.