The 33-year-old is the only player ever to reach a dozen singles titles at the same grand slam after a 6-3 5-7 6-1 6-1 victory over Dominic Thiem.
Thiem had defeated Novak Djokovic in the semi-finals but came away the beaten finalist for the second year in a row.
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Johanna Konta was attempting to become the first British winner of the French Open since Sue Barker – or was she? Eagle-eyed tennis photographer Ella Ling spotted that, for 43 years, Barker has mistakenly had Australia next to her name on the Coupe Suzanne Lenglen. Organisers have said the mistake will be corrected.
Highs and lows
Kristina Mladenovic will not forget June 9 in a hurry. The Frenchwoman began the day by winning her third grand slam doubles title with Timea Babos, completing her media duties just in time to watch boyfriend Thiem lose to Nadal.
Mladenovic was also courtside for Thiem's epic win over Djokovic, and she said: "Someone said, 'You're crazy, you're staying five hours watching Dominic when you're playing tomorrow'. But I feel these moments are exceptional moments that I want to live to the full. It gives me even more adrenaline."