Carli Lloyd, the hero in Beijing four years ago, scored both goals for the Americans.
A year after losing to Japan in the World Cup final, veteran midfielder Carli Lloyd led the top-ranked U.S. team to a 2-1 victory over the Asian nation to earn a gold medal at the 2012 Olympic Games.
Lloyd had both goals for the U.S. on either side of halftime to give the Americans a comfortable lead before Yuki Ogimi got Japan on the board late in the second half.
The U.S. has won gold at the last three Olympics and five times in six final appearances since 1996.
Playing in front of a women's soccer Olympic-record crowd of 80,203 at Wembley Stadium, the Americans took a two-goal lead before Japan made things interesting with less than a half hour to play. For a moment, it looked as though Japan may rally back as it did a year ago.
The two teams met in the 2011 World Cup final, with the Japanese twice coming back to tie the Americans in a match that ended 2-2. Japan then won the title in penalty kicks.
At the Olympics, the U.S. held its own until the very end.
The U.S. controlled the game from the opening kick off and quickly found itself with an early lead thanks to a great interchange play that resulted with Alex Morgan assisting Lloyd for the opening goal.
After receiving a pass from Tobin Heath at the near post, Morgan sent a perfectly placed chipped ball to a rushing Lloyd for a powerful header past goalkeeper Miho Fukumoto in only the eighth minute.
But Japan quickly gained control and would have tied it up had it not been for U.S. defender Christie Rampone getting her foot on a ball with goalkeeper Hope Solo out of position. Moments later, Solo just barely got her hands on a Yuki Ogimi header to deflect it to the crossbar.
The U.S. entered halftime leading 1-0.
In the 54th minute, Lloyd - who had the game-winning goal against Brazil in the final at the 2008 Olympics in Beijing - raced down the middle of the field and drilled a rocket from just outside the middle of the box to give the Americans a two-goal advantage.
Japan got back in the game after a scramble in the U.S. box. Rampone once again bailed out Solo with a stop on the goal line but the defenders were unable to clear the ball and Ogimi was there to put it in the back of the net to assure the Americans wouldn't celebrate too early.
Japan had a huge opportunity to keep its gold hopes alive after Rampone turned the ball over in a very dangerous area, giving Japan's Tanaka an open lane to the U.S. goal. But Solo stepped up to the challenge and made a remarkable diving save.
And the U.S. completed a perfect Olympic run, securing its sixth straight win.