Knock Knock may refer to:

• Knock-knock joke, a type of joke

• Knock Knock (1940 film), an animated short film noted for the first appearance of Woody Woodpecker
• Knock Knock (2007 film), a horror film featuring Stephanie Finochio
• Knock Knock (2015 film), an erotic horror film starring Keanu Reeves
• Knock Knock Live, a 2015 reality TV series
• "Knock, Knock", an episode of the animated TV series The Real Ghostbusters
• "Knock, Knock", an episode of the TV series Six Feet Under
• Knock Knock Woodpecker, a character on the TV series The Great Space Coaster
• "Knock Knock" (Doctor Who), an episode from the tenth series of Doctor Who
• "Knock, Knock" (Gotham), an episode from the second season of Gotham

• Knock Knock (DJ Koze album), 2018
• Knock Knock (Smog album), 1999
• Knock Knock, a mixtape by Misha B, 2013

• "Knock Knock" (Monica song), 2003
• "Knock Knock" (SoFaygo song), 2019
• "Knock Knock" (Twice song), 2017
• "Knock Knock", by the Dazz Band, 1981
• "Knock, Knock", by Dizzee Rascal from Showtime, 2004
• "Knock, Knock", by GZA from Legend of the Liquid Sword, 2002
• "Knock Knock", by the Hives from Veni Vidi Vicious, 2000
• "Knock Knock", by Jasmine, 2010
• "Knock Knock", by Mac Miller from K.I.D.S., 2010
• "Knock, Knock", by Nikki Yanofsky from Little Secret, 2014

• Knock Knock (company), a California-based gift product and book publishing company
• Knock Knock (play), a 1976 play by Jules Feiffer, originally directed on Broadway by Marshall W. Mason
• Knock-Knock (video game), a 2013 video game by Ice-Pick Lodge

• Knock (disambiguation)
• Knock Knock Who?, a 2004 album by Kimya Dawson
• "Knock, Knock Who's There?", a 1970 song by Mary Hopkin
• Knock, Knock, Ginger, a children's game
• Knock Knock Knock, an EP by Hot Hot Heat