An Kum Ae of North Korea won the women's 52-kilogram division by beating Acosta Bermoy of Cuba in a final that went into overtime. An won in the final minutes with a decisive throw that landed Bermoy on her back.
"By winning the gold medal, I think I gave some happiness to our leader Kim Jong Un, so I believe this is meaningful," she said.
A short time later, Georgia's Lasha Shavdatuashvili took gold in the men's 66-kilo category, beating Hungarian Miklos Ungvari in the final with a yuko.
An, who took silver in Beijing in 2008, defeated favourite Masato Nakamura of Japan in her second fight of the day, which helped extend the Japanese gold medal drought for a second day.
Nakamura said she was "full of regret" but said An was simply too strong.
The bronze medals were won by Italy's Rosalba Forciniti and France's Priscilla Gneto.
In the men's final, Shavdatuashvili was frequently on the defensive, almost leaping to avoid the lunging attacks of Hungarian Miklos Ungvari. He often resorted to twisting footwork to get out of Ungvari's attempts to grip his uniform and managed to score a yuko to get the win.
Shavdatuashvili said he hadn't even imagined being at the Olympics a few months ago, as he only recently switched from training as a junior to a senior.
"Since I was young, I have dreamed of going to the Olympics," he said. "I'm very happy to have a medal today."
The top-seeded Musa Mogushkov lost to first-time Olympian Azerbaijani Tarlan Karimov in his first fight.
The men's bronze medals were won by Masashi Ebinuma of Japan and Cho Jun-ho of South Korea.
During a quarterfinal match between the two, the referee and corner judges ruled Cho had won. But after loud boos and jeering from the crowd, a judging panel overturned the decision and made Ebinuma the winner.
Ebinuma later said he thought he had lost the fight.
"There was support from the spectators and I think that allowed me to get the medal," he said, adding he felt a bit bad for Cho.
Cho, meanwhile, said he wanted to focus on the rest of the competition and was happy both men had won medals.