Stéphane Maurice Dion, PC, MP (born September 28, 1955) is a Canadian politician who has been the Member of Parliament for the riding of Saint-Laurent–Cartierville in Montreal since 1996. He was the leader of the Liberal Party of Canada and the Leader of Her Majesty's Loyal Opposition in the Canadian House of Commons from 2006 to 2008. Dion resigned as Liberal leader after the 2008 election where the party suffered their second worst result ever, making Dion only the second Liberal leader in Canadian history who never became Prime Minister.

Dion is a former academic who served as a cabinet minister under Jean Chrétien and Paul Martin and, as such, is a Member of the Privy Council.

Dion was born in Quebec City, Quebec, the second of five children. His mother, Denyse (née Kormann), was a real-estate agent born in Paris, France, and his father, Léon Dion, was a Quebec academic. Dion was raised in a modest home on Liegeois Boulevard in the Sillery district of Quebec City. While growing up, he remembers being taunted for his family's secularism in a society which was then predominantly Catholic.