A former Canadian minister has beaten prominent writer Michael Ignatieff in a leadership election for the country's opposition Liberal party.
Dion won a close race to lead Liberals into the next election.
Mr Ignatieff had been favourite to win the race, but was defeated by ex-Environment Minister Stephane Dion.
Mr Dion's campaign focused on green issues, pledging to act on Canada's Kyoto protocol commitments.
The Liberals lost power last January to the Conservatives led by Prime Minister Stephen Harper.
The BBC's Mike Finnerty at the party convention in Montreal says the election was a nail-biter, as 5,000 delegates struggled to decide who was most likely to beat the Conservatives.
Mr Dion needed four rounds of voting to finally beat Mr Ignatieff, the front-runner.
Mr Ignatieff is a prominent writer, broadcaster and former Harvard academic.
However his 30-year absence from Canada and his initial support for the US-led invasion of Iraq played against him, our correspondent says.
Despite Michael Ignatieff's fame as an author, his support waned.
Mr Dion will lead a party that many have called the natural governing party of Canada because of its dominance in the country's politics.
But a corruption scandal while in office meant the party has spent most of 2006 trying to rebuild.
Environmental issues dominated the Montreal convention.
In his victory speech, Mr Dion made clear he would make the Kyoto Protocol on curbing greenhouse gases a key part of the strategy to win the next elections - which analysts say are likely next year.
Prime Minister Harper has called the Kyoto protocol unrealistic and recently cancelled a meeting with European Union leaders where he was expected to be criticised for his stance.