Mario Dumont (born May 19, 1970 in Saint-Georges-de-Cacouna, Quebec) is a politician in the province of Quebec. He was a Member of the National Assembly of Quebec (MNA), and the leader of the Action démocratique du Québec (ADQ), from 1994 to 2009. After the 2007 Quebec election, Dumont obtained the post of Leader of the Opposition in the National Assembly. Following his party's poor showing in the 2008 Quebec election, he announced his resignation as ADQ leader.
Dumont and his wife, Marie-Claude Barrette, have three children: Angela, Charles, and Juliette.
Dumont bought his first membership card in the provincial Liberal Party at age 15. He stated to his school friends that in the future he would be Quebec's premier. Dumont was a former President of the Parti libéral du Québec's Youth Commission, but had a falling out with the party following the rejection of the Allaire Report proposing maximalist powers for Quebec after the collapse of the Meech Lake Accord.