Andre Ward restored some pride to the US boxing squad by outpointing light heavyweight foe Magomed Aripgadjiev.
The American, who has not lost a decision in six years, won his country's first Olympic title since the 1996 Games in Atlanta.
But the contest was tight, Ward moving ahead only in the third round, which he ended with a three-point lead.
Belarus boxer Aripgadjiev tried to up his work-rate, but was ultimately unable to prevent a 20-13 points loss.
"My eye is hurting a little bit but it's worth it," said Ward.
"I'm fighting bigger, stronger men but somehow, some way I'm coming out victorious.
"I'm just chopping down trees."