Idalys Ortiz claimed Cuba's first Olympic judo title for 12 years as she won the women's heavyweight category at the ExCel Arena on Friday.
Ortiz took a narrow judges' decision over Japan's Maki Sugimoto following a war of attrition. Beijing champion Tong Wen of China had to settle for bronze this time, armlocking Brazil's Maria Altheman.
British veteran Karina Bryant finally landed an Olympic medal at her fourth Games, beating Iryna Kindzerska of Ukraine to bring her 14-year career to a perfect close.
On a day that was initially dominated by a complete outsider, Ortiz helped put the formerly dominant Cubans back on the map.
And she also shattered Tong's image of invincibility, the Chinese fighter not having been beaten by a non-compatriot in five and a half years.
"For me the challenge was to help maintain Cuba's results in judo. We hadn't won a gold medal since 2000 so it means a lot to me," said Ortiz.
"We all prepared well and I've always said no-one is unbeatable and that I could beat anyone, not just Tong Wen."
Teenager Wojdan Shaherkani had made the headlines in the morning session as she became the first ever Saudi Arabian woman Olympian.
The 16-year-old took on Melissa Mojica of Puerto Rico in the first round but was beaten in 82 seconds.
In the early part of the day it seemed as if seven-time world champion Tong would march almost unopposed to a second straight Olympic crown.
She had despatched her first three opponents in double-quick time, the last, Kindzerska, with a brutal armlock.
But in the last four she came unstuck against an inspired Ortiz. The Cuban had upset Russian fourth seed Elena Ivashchenko in the quarter-finals on a penalty and she took another scalp in the last four.
Countering a Tong attack she rolled the Chinese fighter onto her side for a decisive yuko score.
The final was devoid of much excitement as the two fighters cancelled each other out but when it went to the flags, all three favoured Ortiz.
Sugimoto had been impressive early on, throwing Giovanna Blanco of Venezuela and Altheman for the maximum ippon.
Next she faced Bryant, 33, bidding to have one last hurrah in a career that until then had garnered six world medals and seven European medals, including four gold, but never an Olympic gong.
The Briton had turned around a losing position into a victory 12 seconds from the end of her quarter-final clash with Kazakhstan's Gulzhan Issanova with an uchi-mata (inner thigh throw).
Sugimoto beat her by a penalty in a close contest but then Bryant went on to win a hugely entertaining bout against Kindzerska.
The Ukrainian scored a half-point waza-ari, followed by one for Bryant. Kindzerska added a minimum yuko but this time Bryant replied with a second waza-ari, making up a total ippon point and the victory.
It was Britain's second medal of the Games following Gemma Gibbons's silver on Thursday, surpassing the hosts' modest expectations given they had not won one since Sydney in 2000.
"Obviously it means a lot to me, we've had great success over the last couple of days," said Bryant.
"I feel great, I'm particularly happy for myself because it's my fourth Games and this is what I've been after for so long.
"I just kept believing that I could achieve my dream and I'm really happy."