John Munch is a fictional character played by actor Richard Belzer. Munch first appeared on the American crime drama television series Homicide: Life on the Street on NBC. A regular through the entire run of the series from 1993 to 1999, Munch is a cynical detective in the Baltimore Police Department's Homicide unit, and a firm believer in conspiracy theories. He is originally partnered with Detective Stanley Bolander (Ned Beatty). Munch is based on Jay Landsman, a central figure in David Simon's 1991 true crime book Homicide: A Year on the Killing Streets.

Upon the cancellation of Homicide in 1999, Belzer was offered a regular role as Munch on the Law & Order spin-off titled Special Victims Unit. He appeared in the first fifteen seasons of that series from 1999 to 2014, and occasionally as a guest thereafter. On SVU, Munch becomes a senior detective in the New York Police Department's Special Victims Unit, and is first partnered with Brian Cassidy (Dean Winters), followed by Monique Jeffries (Michelle Hurd), and Fin Tutuola (Ice-T). In the ninth season premiere, Munch is promoted to the rank of sergeant and occasionally takes on supervisory functions within the department. In season 14, Munch is temporarily reassigned to the Cold Case Unit, after solving a decade-old child abduction case in the episode "Manhattan Vigil". He returns to the squad in "Secrets Exhumed", in which he brings back a 1980s rape-homicide cold case for the squad to investigate. In the season 15 episode, "Internal Affairs", SVU Captain Donald Cragen (Dann Florek) informs Detective Olivia Benson (Mariska Hargitay) that Munch has submitted his retirement papers, stating that a recent case (portrayed in the episode "American Tragedy") had "hit him hard". In the following episode, "Wonderland Story", Cragen and the squad throw Munch a retirement party, where past and present colleagues and family members celebrate his career. At the conclusion of the episode, Munch returns to the precinct to gather his belongings, where he and Cragen shake hands as Cragen remarks, "you had one hell of a run, Sergeant Munch." Munch has returned, post-retirement, to help his colleagues in the fifteenth-season finale "Spring Awakening" and the seventeenth-season episode "Fashionable Crimes".

The character of Munch has appeared in a total of ten series on five networks since the character's debut in 1993. Apart from Homicide and SVU, however, Belzer's performances as Munch were guest appearances or crossovers rather than regular or recurring appearances. With Munch's retirement in the character's 22nd season on television, he was a regular character on U.S. television longer than Marshal Matt Dillon (Gunsmoke) and Frasier Crane (Cheers and Frasier), both of whom were on television for 20 seasons; he is only behind Mariska Hargitay's character Olivia Benson. Munch's return to help his friends in the SVU seventeenth-season episode "Fashionable Crimes" marks the 23rd season that the character has appeared on television in any capacity. Belzer died on February 19, 2023 after retiring from acting in 2016 and living out his final years in Bozouls, France.