Caroline Wozniacki claimed the biggest title of her career after the Dane staved off a ferocious Venus Williams fightback to take a 6-4 6-4 triumph in the WTA Finals title showdown at a captivated Singapore Indoor Stadium on Sunday.

The 27-year-old former world number one entered the contest having lost to the evergreen Williams seven times in as many matches but the resilient Dane served and retrieved brilliantly and emerged with a deserved victory after 89 minutes.

Wozniacki was faultless for an hour as she raced to a one-set and 5-0 lead but Williams reeled off four games in a row before the Dane could finally lift the title at the elite, eight-woman event in her fifth appearance.

"It was all going well at 5-0 in the second set, then she went for her shots and I was just so happy to get it done in the end," Wozniacki, who will rise three places to third in the world rankings after the win, said in a courtside interview.

"Well eight is my lucky number and I figured if I was ever going to beat her it would be today... and I just went out there and did my best."

The first three games were dominated by the server until the Dane started to find the corners with her powerful backhand and fashioned the first break of the match with back-to-back winners off both flanks.

Williams was trying to get to the net at every opportunity and came forward to good effect after dropping her serve. A vicious cross-court backhand enabled the American to break back immediately on her way to levelling the score at 3-3.

She continued to be the aggressor but the Dane held on in the face of some brutal hitting for her opponent and somehow forged her second break of the set with some exquisite deep hitting to move within one game of taking the opener.

Wozniacki's victory is her second of the season in eight finals after she successfully defended her Pan Pacific Open title in Tokyo last month.