Zou Shiming won his second successive Olympic Games gold medal when he beat Kaeo Pongprayoon in London on Saturday night.
The Chinese veteran won 13-10 against Thailand's Kaeo in the light-flyweight final; a battle between two of the oldest fighters at the 2012 Games.
Britain, Cuba, Japan and Ukraine also won gold medals on the first night of the finals. Ukraine's Oleksandr Usyk won the heavyweight title. Five more finals will be contested on Sunday.
Zou, who had won China's first Olympic boxing medal, a bronze, eight years ago and its first gold in Beijing, added another gold to his three world amateur championships titles.
The canny 31-year-old, who survived a couple of scares to reach the final, grinned all the way to the ring. He was slightly fortunate to be narrowly ahead after the first round.
Pongprayoon, at 32 the oldest among the men's 20 finalists, was cheered on by most of the spectators. The cheering turned to boos after the second round, which he was again unlucky to lose by a single point.
Pongprayoon caught Zou with a big left in the final round, but the now double Olympic champion, who was warned for holding, hung on to win.
Pongprayoon, who also received a warning in the final seconds of the bout, fell to the floor in tears and beat the canvass in frustration as a flag-waving Zou was announced as the winner.
Losing semi-finalists Ireland's Paddy Barnes and David Ayrapetyan of Russia won the bronze medals.
CAMPBELL TAKES BANTAMWEIGHT GOLD
Britain's Luke Campbell emulated his female team-mate Nicola Adams when he beat John Joe Nevin or Ireland 14-11 in the bantamweight final.
Campbell, who also beat Nevin in the semifinals of last year's world championships, knocked the Irishman down in the final round to seal the victory.
The first round was among the best at the London Games. Campbell, counter-punching well, took it by two points.
Nevin caught the 24-year-old Briton with the tougher shots in the second round to close the gap to a point.
But there seemed little doubt about the result halfway through the final round when Nevin was knocked down by a right hook.
Campbell was close to tears as he awaited the verdict and could hold them no longer when the result was announced.
Lazaro Alvarez Estrada of Cuba and Satoshi Shimizu of Japan took bronze.
CUBA'S FIRST GOLD IN EIGHT YEARS
Roniel Iglesias Sotolongo of Cuba won the light-welterweight gold medal when he won 22-15 against Ukraine's Denys Berinchyk.
Sotolongo won his country's first Olympic boxing gold medal in eight years. He was one of four Cuban bronze medallists at the Beijing Games.
The 2009 world champion, who will celebrate his 24th birthday on Tuesday, took the first round 5-4 after knocking Berinchyk down, and maintained his work rate to take the second 6-5.
Berdych was outclassed in the third as Iglesias upped the pace and finished by taking the round 11-6.
Mongolia's Munkh-Erdene Uranchimeg and Italy's Vincenzo Mangiacapre won the bronze medals.
JAPANESE WINNER AFTER 48 YEARS
Ryota Murata won Japan's first Olympic Games boxing gold medal for 48 years when he took the middleweight title, winning 14-13 against Brazil's Esquiva Falcao.
Japan's last boxing gold medal at the Olympics was won by Takao Sakurai in Tokyo in 1964.
Falcaos brother Yamaguchi won bronze in the light-heavyweight division. But Murata denied Brazil a first Olympic Games boxing gold medal. Brazils only boxing medal before the three they won in London came in 1968.
The 26-year-old Murata, a silver medallist at last year's world championships, countered superbly in the first round to open up a two-point lead.
Falcao cut that back to a single point after the second round thanks to a couple
