Lightweight Robson Conceicao became Brazil's first ever Olympic boxing champion when he was given a unanimous points decision in his final against Frenchman Sofiane Oumiha.
Conceicao took the host nation's tally of gold medals to three in Rio after he was given the verdict 30-27 29-28 29-28 in a 60kg showdown at an electric Riocentre on Tuesday.
The Salvador-born 27-year-old's success gave Brazil a second successive night to remember after Thiago Braz da Silva claimed a sensational victory in the pole vault.
Julio Cesar La Cruz will face Kazakh fighter Adilbek Niyazymbetov in the final of the men's light heavy (81kg) final after they were both awarded unanimous decisions on day 11.
Cuban La Cruz is guaranteed at least bronze after he outpointed France's Mathieu Bauderlique, while Niyazymbeto came out on top against Great Britain's Joshua Buatsi in the second semi-final.
Nicola Adams earlier started the defence of her fly (48-51kg) title by beating Tetyana Kob of Ukraine on points to reach the semi-final.
An emotional Conceicao entered the history books in his homeland after rising to the occasion to deny Oumiha gold.
Conceicao went on the offensive from the first bell and played to a partisan crowd with some showboating with victory in his grasp.
He sunk to his knees and roared by his supporters following an impressive display of boxing under pressure.
QUOTES OF THE DAY
"Of course my life has changed, it is the most incredible day in my life. This medal is not only for my coach but for myself and family ... I'm Olympic champion." - Conceicao revels in his finest hour.
"It will be a really big change for me because I will be the first boxer to win gold in this division ever in the history of Cuba so it will be a really big change for me and my family. Financially and in general." - La Cruz on what it would mean to win gold following his semi-final victory.
"It's the first time I've fought in front of a crowd like this but it was magnificent. The Brazilian public were so behind him. If it had been in France, it would have been the same for me." - Oumiha had no complaints with the crowd following his defeat to the home favourite.
Shakhram Giyasov of Uzbekistan and Kazakhstan's Daniyar Yeleussinov will contest the men's welterweight 69kg final on Wednesday. The women's 57-60kg semi-finals also take place on day 12.