Marina Alabau Neira won gold in the women's RS:X windsurfing in Weymouth.
She led going into the medal race and won the finale with Finland's Tuuli Petaja in silver and Poland's Zofia Noceti-Klepacka in bronze.
Britain's Bryony Shaw had only an outside chance of a medal going into the last race and, despite a fourth, could only finish seventh overall.
"It's not to be a medal this time. I'm gutted, but it's been a great journey," said Shaw, who won bronze in Beijing.
Shaw, 29, had one win and no result worse than ninth in the 11-race series, but despite her consistency she was unable to make inroads into the podium places.
She ended on 59 points, 12 points off the bronze medal position.
Spain's Alabau Neira had four wins and four other top-three finishes to win by 20 points.
"I'm super-happy, super-excited," she said.