Adonis Stevenson knocked Chad Dawson down with a left hook in the first round to claim the WBC light heavyweight title on Saturday night.
Stevenson (21-1), a power puncher from Longueuil, Que., sent a crushing left to Dawson's temple less than two minutes into the scheduled 12-round bout.
Dawson (31-3-0) got up, but referee Richard Griffin checked his eyes and declared the bout over with the dethroned champion looking wobbly on his feet.
The delirious Bell Centre crowd jumped up and sang the Ole Ole song fans use at Montreal Canadiens hockey games.
Stevenson became the only Canadian boxer currently with a world title. He did it on his first attempt.
Dawson was in his 11th title fight. He had held the WBC belt twice, taking it most recently last year from veteran Bernard Hopkins.
The New Haven, Conn., native was also beaten by former WBC champ Jean Pascal of Laval, Que., on a visit in 2009.
The bout between lefthanders was billed as a match-up of Dawson's skill and ring savvy against Stevenson's power
In the co-feature, Yuriorkis Gamboa won the interim WBA lightweight title with a unanimous decision over Darleys Perez in a bout that had fans booing the lack of action.
Gamboa (23-0), the 2004 Olympic gold medallist from Cuba who now lives in Miami, snuck a left hook around Perez's guard for a knockdown in the opening round and never trailed in the bout.
It was Gamboa's first fight as a lightweight after holding titles at featherweight and junior lightweight. Perez (28-1) was in his first title bout.
He was led into the ring by his promoter, rapper Curtis (50 Cent) Jackson.
But fans grew impatient with long stretches of inactivity from both fighters, with the larger Perez keeping his distance and the quick-handed Gamboa seemingly content to sit on his lead.
Two ringside judges had it 116-111 and the other 115-112, all for Gamboa. The Canadian Press scored it 116-111 for Gamboa.
It was no contest as middleweight David Lemieux (29-2) of Montreal knocked down Poland's Robert Swierzbinski (11-2) once with a right to the body and twice with left hooks in the first round for a quick win.
HBO put a super-featherweight bout between Jose Pedraza of Puerto Rico against Mexico's Sergio Villanueva and it got the crowd going as Pedraza (13-0) stopped Villanueva (25-3-2) in seven rounds with a barrage of body shots.
Promoter Yvon Michel's new signing, two-time Olympian Artur Beterbiev of Russia, easily won his pro debut as he stopped Christian Cruz (12-16-1) in the second round of a light heavyweight bout. Cruz has lost 11 in a row.
Heavyweight Didier Bence (9-0) of Montreal also stopped Eric Barrak (7-1) of St-Come, Que., in the second.
A tight welterweight bout saw Sebastien Bouchard (7-0) of Quebec City eke out a six-round unanimous decision over Frank Cotroni (7-1) of Montreal.