Martin Cauchon (born November 21 1962) is a Canadian politician and former Liberal Party of Canada cabinet minister.

Cauchon was born and raised in Quebec where he became a lawyer. He first entered politics when he ran against Prime Minister Brian Mulroney in the riding of Charlevoix in the 1988 Canadian election and was defeated. He first won a seat in the Canadian House of Commons in the 1993 Canadian election in the riding of Outremont and was re-elected in 1997 and 2000.

Cauchon was appointed Secretary of State for the Federal Office of Regional Development - Quebec by Jean Chrétien in 1996. He became a full cabinet minister in 1999 when he was given the position of Minister of National Revenue. On January 12 2002 he became Minister of Justice and Minister with political responsibility for Quebec. As justice minister, Cauchon argued in cabinet in favour of same-sex marriage and the decriminalization of marijuana.

Cauchon was a Chrétien loyalist and opposed Paul Martin's attempt to force Chrétien to retire. When Chrétien did announce a date for his resignation, Cauchon was touted as a possible candidate to succeed him but did not end up running in the 2003 Liberal leadership convention. Cauchon refused to back Martin's leadership bid, instead supporting John Manley, and was not included in Martin's first cabinet. Cauchon did not run in the 2004 Canadian election. There have been reports that he is either organizing an attempt to remove Martin as Liberal leader or a leadership campaign to succeed Martin when he retires.