Codename: Kids Next Door is an American animated television series created by Mr. Warburton for Cartoon Network. The series follows the adventures of a diverse group of five children who operate from a high-tech treehouse, fighting against adult and teenage tyranny with advanced 2×4 technology. Using their code names (Numbuhs 1, 2, 3, 4, and 5), they are Sector V, part of a global organization called the Kids Next Door.

The series' pilot premiered on Cartoon Network in mid-2001 as part of The Big Pick II, a special broadcast event showcasing 11 pilots for different series. The winner of a viewers' poll by Cartoon Network would decide which pilot would be greenlit to be a full series. After winning the poll, the series premiered on December 6, 2002, and concluded on January 21, 2008, after six seasons and 81 episodes. Two television films were broadcast: Operation: Z.E.R.O., which aired in 2006, and Operation: I.N.T.E.R.V.I.E.W.S., which aired as the series finale in 2008. A special half-hour crossover episode with fellow Cartoon Network series, The Grim Adventures of Billy & Mandy, aired in 2007.

Spin-off media include two video games, Operation S.O.D.A. and Operation V.I.D.E.O.G.A.M.E., as well as a trading card game, comic books, and DVD releases. Codename: Kids Next Door has also appeared in DVD anthologies and compilation video games from Cartoon Network.