"Mama Said Knock You Out" is a number-one hit single by LL Cool J from his album of the same name. The song famously begins with the line "Don't call it a comeback/I've been here for years." Before "Mama Said Knock You Out" was released, many people felt that LL Cool J's career was waning; his grandmother, who still believed in his talent, told him to "knock out" all his critics. The song was produced by Marley Marl with help from DJ Bobcat along with LL. The single reached number 17 on the Billboard Hot 100, was certified Gold by the RIAA, and won the Grammy Award for Best Rap Solo Performance. The song takes various shots at Kool Moe Dee.

The song was featured in the Michael J. Fox action comedy The Hard Way, in which LL Cool J also appeared.

The song uses samples from James Brown's "Funky Drummer," the Chicago Gangsters' "Gangster Boogie," Sly & The Family Stone's "Trip to Your Heart" the drum break from Digital Underground's "The Humpty Dance", and LL Cool J's own "Rock the Bells". The music video features LL Cool J in a boxing ring, rapping into a microphone similar to the one an announcer would use in a boxing match. Intercut with this are clips of boxing matches and LL Cool J exercising.

LL Cool J said in his autobiography that the idea for the song came from a discussion with his grandmother. He had said to his grandmother that he felt that he couldn't survive as a rapper now that gangsta rap was popular and he was being dissed by several up-and-coming rappers. She responded, "Oh baby, just knock them out!" She is featured in the closing scene of the music video, saying: "Todd! Todd! Get upstairs and take out that garbage."

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