Marie-Philip Poulin of Canada got the gold medal winning goal, which put the team over USA at the 2014 Olympics.
Canada had a 4 on 3 power play at the time of the goal.
Poulin, a 22-year-old forward, currently plays for the Boston University Terriers.
She was also on the gold medal winning team at the 2010 Olympics in Vancouver.
Canada trailed 2-0 before Brianne Jenner and Poulin scored in the final 3:26 of regulation, and Poulin had the game-winner with a power play goal at 8:10 of overtime.
Shannon Szabados made 27 saves for Canada, which has won 20 straight in the Winter Games since the Nagano final in 1998. That was the only gold medal for the United States, which has lost in the Olympic final to Canada three times since then.
Jessie Vetter made 28 saves for the Americans. Meghan Duggan and Alex Carpenter scored for the U.S.
Switzerland beat Sweden for the bronze medal earlier Thursday.
Vetter, the loser in the Vancouver final, had a shutout until Jenner’s seemingly harmless shot deflected off a defender’s knee and into the net. With the goalie pulled for an extra skater, U.S. forward Kelli Stack sent the puck the length of the ice before it clanged off the post and landed harmlessly in front of the goal.
It was still a one-goal game, but not for long.
With Szabados still off, Poulin scored just 54.6 seconds before the end of regulation.
After six tense minutes of overtime, the U.S. picked up a power play when Catherine Ward was sent off for cross-checking. But five seconds later, Jocelyne Lamoureux was called for slashing for swiping at the goalie’s pads after a save. And during a bad player change by the Americans, five-time Olympian Hayley Wickenheiser got free on a breakaway before she was bumped from behind by Hilary Knight and sent sprawling.
It could have been called a penalty shot. It could have been no call.
But Knight was sent to the penalty box for cross-checking. With the 4-on-3 advantage, the Canadians worked the puck around and over to Poulin, who knocked it into the open net and set off the celebration on the bench and among the Maple Leaf-waving fans.
Poulin has been called the Sidney Crosby of women’s hockey for being so young yet achieving so much already. She played during the 2007-2008 season with the Montreal Stars in the Canadian Women’s Hockey League, and a year later helped the Stars win the Clarkson Cup.
She is a co-captain on the Terriers, which she joined in 2010.
The Associated Press contributed to this report.