Dennis Paul Drainville (born February 20, 1954 in Joliette, Quebec) is a Canadian priest and politician. He was a member of the Legislative Assembly of Ontario from 1990 to 1993, and later became Quebec leader of the New Democratic Party.

Drainville was educated at the University of Toronto's Trinity College, and became an Anglican priest after his graduation. He worked as a parish priest in Ontario from 1982 to 1984, and was the executive director of STOP 103, a multi-service agency in Toronto, from 1984 to 1986. He has served as a priest in the Anglican dioceses of Montreal and Toronto.

He first ran for the Ontario legislature in the 1977 provincial election. Drainville was a member of the Liberal Party at the time, and campaigned in the downtown Toronto riding of Riverdale . He finished a distant third against the winner, Jim Renwick of the New Democratic Party.

Drainville himself later joined the NDP, and in the late 1980s was arrested for protesting the province's clearcutting practices in the Northern Ontario forests around Temagami. Drainville was NDP candidate in the riding of Victoria—Haliburton in the 1990 provincial election. This east-central Ontario seat was not regarded as winnable – indeed, no NDP candidate in the riding had ever finished higher than third place, behind the Liberals and Progressive Conservatives. However, the NDP under Bob Rae won an unexpected majority government in the election, and Drainville won the riding by 6,520 votes over his nearest opponent.

Drainville served as a parliamentary assistant from 1990 to 1992, and as a Deputy Speaker from 1992 to 1993. His loyalty to the Rae government became increasingly tenuous during this period, however. Drainville emerged as an ally of Peter Kormos in the NDP caucus, and frequently opposed the policies of the Rae government from a left-wing perspective. On April 28, 1993, he resigned from NDP caucus to protest the Rae government's decision to bring casinos into the province. He continued to sit in the legislature as an independent. Later in the year, he voted against the Rae government's Social Contract legislation.

Drainville resigned from the legislature on September 27, 1993, and declared himself an independent candidate in the 1993 federal election. He finished a distant fourth against Liberal John O'Reilly in the federal Victoria—Haliburton riding, though he did outpoll the official NDP candidate by over a thousand votes. Following the election, he worked as the general manager of a contracting company.

Drainville later realigned himself with the federal NDP, and became the leader of its Quebec wing. He ran as an official NDP candidate in the 1997 election in the Quebec riding of Bonaventure—Gaspé—Îles-de-la-Madeleine—Pabok , but again finished a distant fourth with only 649 votes. It may be noted that the NDP has long been relatively weak in Quebec, particularly since the emergence of the Bloc Québécois, and such a finish was not uncommon.

Drainville was elected to the Council of the General Synod of the Anglican Church of Canada in 2004, at a meeting in St. Catharines, Ontario. At the same meeting, he seconded a successful motion for the Anglican Church in Canada to affirm the unions of same-sex couples.