Williams finally added the season-ending title to her list of achievements
Venus Williams won the WTA Tour Championships for the first time in her career with victory over Russia's Vera Zvonareva in Doha on Sunday.
The American won 6-7 (5-7) 6-0 6-2 to claim her 39th career title and first at the season-ending championships.
Zvonareva edged a dramatic opening tie-break from 5-1 down, taking it with a net cord, but Williams stormed through the second set.
And her domination continued as she won 12 of the last 14 games for victory.
"I'm so excited," said Williams. "It was a hard-fought match right down to the end, we were both wanting it so bad. I'm glad I got it."
Zvonareva said: "I think I could have done better today and obviously I'm a little bit disappointed.
"But it's the first time I'm able to win so many matches in a row against top-10 players and I'm just looking forward to next year."
Next year the ranking system is going to be a little bit different and it might help quality over quantity
Zvonareva, 24, came into the event as the lowest-ranked player at ninth in the world.
But she swept through her round-robin group, beating Svetlana Kuznetsova, Ana Ivanvovic and world number one Jelena Jankovic, before seeing off Elena Dementieva in the semis.
Williams was in equally good form, arriving in the final on the back of an eight-match winning streak that included a comeback win over her sister Serena on Thursday.
But it was the Russian who started the better, breaking serve at the first opportunity and coming through a lengthy following game to consolidate.
However, when she failed to serve out the set at 5-3, letting a set point slip by, her chance appeared to have gone and Williams raced 5-1 clear in the tie-break.
The American had not been at her best though and unbelievably she allowed Zvonareva to reel off six straight points, the last coming with a net cord that left Williams stranded.
Williams was clearly not amused and there was a hint of anger in the way she stormed through eight successive games to seal the second set and move clear in the decider.
Zvonareva stopped the rot by breaking back to trail 2-1 but it was only a temporary respite, and Williams broke twice more on her way to serving out the match.
Williams admitted that losing the opening tie-break from 5-1 up had been a blow but was pleased with the way she recovered.
"Sometimes it goes your way and all of a sudden it comes crashing down but I thought 'it's not over yet' - that's the best thing about tennis," she said.
"This puts me in a great position to keep climbing the rankings next year.
"I'm hoping to stay healthy and I think I can only go higher. We (Venus and her sister) don't play as many tournaments as other players - it's not what we do.
"Next year the ranking system is going to be a little bit different and it might help quality over quantity."
Cara Black of Zimbabwe and American Liezel Huber beat Rennae Stubbs of Australia and Kveta Peschke of Czech Republic 6-1 7-5 to win the doubles title.