Sarah Menezes became the first Brazilian woman to win an individual judo gold at an Olympic Games with victory in the under-48kg final.
The second-seeded Menezes dethroned reigning Olympic champion Alina Dumitru of Romania in the final.
Menezes had been frustrated but landed the winning throw in the final minute.
Earlier, Hungarian fighter Eva Csernoviczki recovered from being strangled unconscious to claim an unlikely bronze medal.
Csernoviczki was rendered unconscious as she tried to resist a strangle in her quarter-final loss to Belgium's Charline van Snick.
Having lost in the quarter-final, she was given a second medal chance in the repechage.
She then defeated China's Wu Shugen and then stunned world number one Tomoko Fukumi with a foot sweep in a sudden-death golden score period to earn a podium finish.
Van Snick later won the other bronze medal, defeating Argentina's Paula Pareto.