Swiss world No. 2 Roger Federer defeated archrival Rafael Nadal in three sets, becoming the final winner of the ATP World Tour Finals on Sunday.

It's the fifth time that the 16 Grand Slam titles holder was crowned at the season finale.

"It's fantastic. I'm really thrilled the way I played all week," said Federer. "I'm just really happy the way I was able to finish the season in style, playing some of my best tennis, really saving the best for last."

Federer, 29, has been in stunning form by winning all three group matches and the semifinal without losing a set. He continued to dominate the court in the O2 Arena by taking the first set 6-3 against world No. 1 Nadal, but was broke in the second set by the Spaniard to concede a set 6-3.

"I think the game I got broken, I hardly made any first serves," said Federer. "He was able to find a way to break me in that game. So I just really tried to focus harder on my first serves to make sure I make them, just focus even more of doing the right things. Then I knew that I could come through."

Federer kept his sharpness in the deciding set while the 24-year-old Nadal revealed sign of tiredness as he fought three hours and 11 minutes to send off British top Andy Murray in the semifinal on Saturday.

After breaking twice, Federer won the final set 6-1 so as to become the third player in the tournament's 41-year history to win the title five times, joining Ivan Lendl and Pete Sampras.

"He played unbelievable," Nadal commented on Federer, who reached nine finals this year and won seven times. "He played unbelievable during all the week, so his level was very high. I try my best this afternoon, but he was better than me."

But Nadal, reaching the final of the season finale for the first time was satisfied enough with his result in London. "I'm more happy about all the week. It's a fantastic week for me, winning four top eight players in the same week in a difficult surface for me. I think it has never happened before, so that's very good news for me."