Jeeno Thitikul of Thailand capped off her best year with the biggest cash prize in women's golf.
She held off an early challenge from Pajaree Anannarukarn and closed with a four-under 68 to win the CME Group Tour Championship.
That saw her claim the $4m pay-off that comes with winning this title once again.
The victory also assured her of winning the LPGA player-of-the-year award and the Vare Trophy for the lowest scoring average, the two biggest awards in women's golf.
Thitikul won for the third time this year on the LPGA Tour, and one last birdie on the final hole at Tiburon Golf Club gave her the lowest scoring average in tour history.
This was never really in doubt when Thitikul started with a six-shot lead over Nelly Korda, the American she replaced at No 1 in the women's world ranking this year.
Anannarukarn made it a game, however, with five birdies in seven holes to pull within two shots going to the back nine.
Thitikul birdied the 10th and 13th holes, while her fellow Thai dropped a shot on the par-three 12th to return the lead to five shots.
From there, it was getting to the finish line for a celebration on the 18th green. She joins Jin Young Ko as the only back-to-back winners of the CME Group Tour Championship.
Thitikul finished at 26-under 262 for a four-shot victory.
Korda becomes the first player since Tiger Woods in 2010 to go from a seven-win season to not winning the following year.
