Daniil Medvedev claimed his first Association of Tennis Professionals (ATP) Paris Masters title after coming from a set down to end Alexander Zverev's 12-match winning streak.
The Russian beat Zverev of Germany 5-7, 6-4, 6-1 to secure the third ATP Tour Masters 1000 crown of his career.
The triumph will see him replace Swiss star Roger Federer as the world number four.
Both players dominated their service games in the opening set until Zverev made the decisive break in the 12th game.
Medvedev won a 38-shot rally on his way to his first break point opportunity of the match in set two, and the game lasted 15 minutes with Zverev saving four break points.
But Medvedev finally broke Zverev’s resistance, taking the second set in 51 minutes before bursting into a 4-0 lead in the decider.
The 24-year-old then wrapped up the victory when Zverev double faulted.
"It’s great, I’m really happy," said Medvedev, who now has won eight ATP Tour titles.
"As I always say, I don’t celebrate after the match but I’m really happy to win matches.
"Before the tournament I was not in my best form with zero finals this year.
"Finally I’m the winner of a tournament that I love and first title in France."
Zverev, who won back-to-back titles in Cologne in Germany last month, admitted fatigue caught up with him once Medvedev raised his level in the second set.
But the German believes he has enough time to recover before the ATP Finals - due to take place from November 15 to 22 in London.
"Once you get a little bit tight against him, he wears you down and wears you down even more," said Zverev.
He makes you run and move.
"He's a great player.
"It's his first tournament win of the season.
"I know his season wasn't the easiest one, whereas I have to say my season is actually going quite well.
"We will see how it goes with London.
"I'm happy with my tennis, I just need to maybe recover a little bit physically."
Medvedev has also qualified for the ATP Finals.