Face bruised and starting to swell, an open cut over his left eye, Robson Conceicao cannot stop grinning as he dissects the nine minutes of his boxing match and the 27 years that have brought him here.

He is now an Olympic champion, Brazil's first in the sport, after defeating Frenchman Sofiane Oumiha in a unanimous decision in the lightweight final on Tuesday night in front of a baying partisan crowd that would not look out of place at the city's iconic Maracana Stadium.

He is a symbol of inspiration for many of the country's impoverished, having been raised in the streets of Salvador in the north-eastern state of Bahia where he sold melting popsicles to motorists waiting at traffic lights.

With the Brazilian flag tied around his shoulder like a cloak - to almost everyone inside the 9,000-capacity Riocentro Pavilion 6 he was a superhero - he said in Portuguese: "My life has changed forever with this, this is an incredible moment in my life. It was an incredible feeling to represent the whole of Brazil. I still feel like I'm in a dream and none of this is real."

But the gold medal he bit into was undeniably his after a thrilling and aggressive performance that caught his opponent by surprise as much as the intimidating atmosphere did.

"He had the whole country, his people, behind him," said Oumiha, an unheralded 21-year-old from Toulouse.

"It was a magnificent crowd. I thought I was ready for it but it was still an experience. He was the better boxer tonight."

Conceicao picked up boxing almost 20 years ago and at the beginning was so poor that he faked arm injuries at hospitals to get bandages needed to tape his hands for training and used slippers as punching pads during sparring.

Brazil had won only one silver and three bronze medals in boxing at the Summer Games since first competing at the 1948 London edition and Conceicao, who suffered first-round exits at the last two Olympics, began the 60kg championship bout in a hurry.

His every punch and every sidestep was greeted by wild cheers as fans - some dressed in mock boxing gear like bath-robes, head protector and gloves - chanted "E campeao! (He's champion!)" and "Robson!" throughout each of the three-minute rounds.

"I knew I had to come after him, because he is so good on the counter-attack and there was no way I wouldn't be punched," said Conceicao, who finished second and third at the 2013 and 2015 world championships respectively. "The goal was to receive one punch, and then land three or four on him."

He claimed the first two rounds on all three judges' scorecards and held off Oumiha in the third before falling to his knees when he was announced the winner.

Cuba's three-time world champion Lazaro Alvarez, beaten by Conceicao in the semi-finals, and Mongolia's Dorjnyambuugiin Otgondalai took bronze.

Brazil coach Claudio Aires paid tribute to the supporters: "Nothing can be built by one person and this victory was the result of many."

Chief among them has been Conceicao's wife Erika Mattos, a former boxing Olympian herself, and his daughter Sofia, who turns two tomorrow and whom he had promised the gold medal.

When asked by The Straits Times what he would say to her when she was old enough to understand the significance of this triumph, Conceicao's smile widened: "I will tell her that she was my biggest inspiration and that I wanted to give her the biggest gift that I could."