Elina Svitolina came from one set behind to beat 2017 US Open winner Sloane Stephens and claim the 2018 WTA Finals in Singapore.
The season-ending championship was the Ukrainian's biggest career title and her fourth this year, after Brisbane, Dubai and Rome.
Svitolina won 3-6, 6-2, 6-2 in two hours and 23 minutes after a memorable match.
The 24-year-old won all five of her matches on the hard court, becoming the first player to go undefeated at the tournament since Serena Williams in 2013.
But it was the fifth-seeded American who claimed the first set.
On-court coaching brought an intriguing element to the match.
At 3-0 down Svitolina was struggling, and her coach clearly had a hand in her pulling it together:
"Calm down, breathe, go after the ball when it’s in the court, hang in there when it’s out, and attack the second serve, you're being too passive..."
Svitolina listened and bit by bit she worked her way back into it.
Svitolina had played the longest match of the tournament the day before the final, but she looked sharper than Stephens.
The number six seed had the fans off their seats with some impressive shots.
Perfect ending for Svitolina
Stephens pulled it back to 3-2, but was unable to get any closer, as her Ukrainian rival closed in on victory at 5-2.
Suddenly it was all over: a shanked forehand sent Svitolina collapsing onto the court in joy.
"It is amazing. I am very pleased with my performance this week"
Svitolina hasn't lost a final on the WTA Tour in the last two seasons.
"There were nerves early on but I was just trying to fight for every ball and I think that made the difference in the end. Sloane played amazing tennis so I really had to play my best tennis to win," added Svitolina.
Stephens, meanwhile, was taking the loss in her stride:
"It is not the way I wanted to finish but I worked really hard to get here and I can be really proud of my result today."
After five years in Singapore, the WTA Finals will be held in Shenzhen, China next year.
You can watch the full match highlights here: