Britain's Mark Lewis-Francis held off the USA's Maurice Greene on the last leg to win a stunning gold medal in the men's 4x100m relay.
Jason Gardener, Darren Campbell, Marlon Devonish and Lewis-Francis were faultless with their baton changes as they stunned the pre-race favourites.
Britain clocked 38.07 with the USA one hundredth of a second behind, and Nigeria taking the bronze.
The USA bid stumbled with a poor change between Justin Gatlin and Coby Miller.
"It's been emotional," said Campbell, who had been criticised over his performances by American athletics legend Michael Johnson.
"I just tried to let my feet do the talking."
Gatlin, the 100m champion, took over from 200m gold medallist Shawn Crawford but fumbled his handover to Miller leaving Britain ahead going into the final bend.
Lewis-Francis, who failed to reach the final in the individual 100m, put in a sensational effort to stay ahead of the fast-finishing Greene, the 100m bronze medallist and former Olympic champion.
It is the first British Olympic relay gold medal since 1912.
Britain were almost disqualified from the semi-final after a sloppy third baton change but Lewis-Francis insisted their team bond drove them to victory.
"With the team spirit that we had we knew we could come back stronger and we proved everyone wrong," he said.
the greatest thing that has ever happened to me in my whole
life. I knew I had it won as soon as I got the baton."
Gardener, who ran the first leg, added: "It's a dream come true. We had amazing faith in each other after the semi-final. I can't take it in at this moment in time."
Greene said aferwards: "I gave it my all. But Great Britain put on a
great show tonight."
Britain took silver behind the USA in the 2003 World Championships but were later stripped of their medals when Dwain Chambers failed a drugs test.
And the men's sprinters had been under pressure given there was no representative in either the 100m or 200m Olympic finals for the first time since 1976.
But after Saturday's relay victory, Lewis-Francis concluded: "I can go
home with my head held high even though my individual race didn't go to plan.
"I am an Olympic champion, it is the greatest thing ever to happen to me in my life."