Amelie Mauresmo rallied from a set down to beat compatriot Mary Pierce 5-7 7-6 6-4 in the WTA Championships final.
Mauresmo kisses the Championship trophy
In an epic contest that lasted three hours and six minutes, Mauresmo's strength and athleticism were key.
Pierce had the chance to break back in the final game at 0-40 on Mauresmo's serve, but made five unforced errors in a row to hand the match to her rival.
Mauresmo said: "I wanted to make her work and that's what I did from the start. That paid off in the third set."
The Fed Cup team-mates traded early breaks in the first set before the 30-year-old Pierce gained a vital 6-5 lead when Mauresmo missed a forehand.
Pierce was able to serve out the set when Mauresmo missed another forehand.
Mauresmo, fiercely determined, broke early in the second set to build a 3-1 advantage.
Although Pierce rallied to take the set to 6-6, the 26-year-old was too strong and took the tie-break 7-3.
The two traded early breaks in the deciding set, but Mauresmo began to get the better of their longer rallies and eventually took the title thanks to Pierce's dramatic capitulation.
Mauresmo said she had confounded some of her critics after clinching the biggest title of her career.
She said: "So many people said I couldn't win. I'm so glad I went through this moment. Hopefully there will be many more like this.
"You have moments when you believe that it is going to happen and some moments when your mind is down a little.
"You think to yourself, 'I'm never going to do it.'"
Mauresmo will now move up a spot to number three in the rankings, while Pierce will end the year ranked five.