Ben Ainslie joined Rodney Pattison as Britain's most successful Olympic yachtsman by taking gold in the Finn class in Athens on Saturday.
The 27-year-old, already assured of silver, needed to finish within 15 places of Spaniard Rafael Trujillo.
He crossed the line in 14th place, just behind Trujillo, to maintain Britain's medal charge on the Saronic Gulf.
Ainslie added gold to the silver and gold medals he won in the Laser class in 1996 and 2000.
"This one feels quite different from Sydney, with the way the whole event worked out," he said.
"But getting another gold medal is just an amazing feeling. I am so happy."
Ainslie followed Shirley Robertson's lead in claiming Britain's second sailing gold of the Games.
Like Robertson, he switched to a different boat after Sydney, but dominated his rivals in the Finn despite being disqualified in the second race.
Since finding himself 19th after that first day, Ainslie has posted four victories, two second places, a third and a fourth.
"Day One was a bit of a disaster so to come back and win gold after that is unbelievable," Ainslie added.
He made a cautious start in Saturday's final race, passing the first mark seven places behind Trujillo.
He eventually came home in 14th place, almost alongside Trujillo, who took silver.But he covered the Spaniard's every move and took a tight line inside the third mark to keep his main rival within striking distance for the rest of the race.
"I might have looked relaxed but I was actually incredibly nervous," Ainslie explained.
"The wind was very light, almost unsailable, and a lot can happen in those conditions.
"But I just tried to stay with the Spanish guy and it worked out well for me."
Ainslie ended the competition with 38 points, 13 ahead of Trujillo.
Poland's Mateusz Kusznierewicz won the final race to claim the bronze medal.