Decker is an American comedy web series and series created by Tim Heidecker and Gregg Turkington. The show is a web spinoff/tie-in to the series On Cinema at the Cinema and began on July 17, 2014. Many recurring jokes and the personas and mutual antipathies expressed by Decker and Turkington carry over from the relationship of the "real" actors, Heidecker and Turkington, in On Cinema.

The series is a spoof of action films, with intentionally bad production for comedic effect. It focuses on Special Agent Jack Decker (Heidecker), who attempts to stop terror attacks before they occur. At his side is Special Agent Kington (Turkington), with recurring appearances from many guests of the On Cinema series, such as Joe Estevez as President Davidson, and Mark Proksch as Abdul.

The series is part of the "On Cinema universe" which has a cult following, especially through social media. In response, Heidecker and Turkington started Decker-Con, where new episodes of Decker are screened and the cast appears as their "On Cinema" characters, meeting and talking to fans.

Initially an Adultswim.com series, it was announced to be moving to TV on December 17, 2015, and its fourth season premiered on June 17, 2016, on Adult Swim. The series was renewed for a fifth and sixth season, both of which aired in 2017.