Zimbabwe's Kirsty Coventry added gold to her silver and bronze medals by storming to victory in the women's 200m backstroke final in Athens.
The silver 100m backstroke and 200m medley bronze medallist never relinquished her lead and won in two minutes, 09.19 seconds.
Stanislava Komarova of Russia took the silver with joint bronze for Antje Buschschulte and Reiko Nakamura.
Britain's world champion Katy Sexton finished a disappointing seventh.
The 22-year-old had the third fastest time in the world leading into the Games and was tipped as a serious medal contender.
But Sexton admitted she was struggling for confidence and finished in 2:12.11 - more than three seconds off her British record.
"To not compete how I expected and not get what I feel I deserved at the
Olympics is just really really upsetting," said Sexton.
"It's going to be a lot tougher to get over this because it's an Olympic Games and they only come round every four years.
"It's just really hard when you know how much work you've put in but I'm sure I'll bounce back."
Coventry will return to Zimbabwe with their first-ever swimming gold medal.
The 20-year-old opened up a narrow lead over Buschschulte but pulled away to win by half a body length.