Third seed Alexander Zverev eased past home favourite Ugo Humbert 6-2, 6-2 in the Paris Masters final on Sunday and will return to his career-high number two in the world rankings.
German Zverev will leapfrog Carlos Alcaraz in Monday's official rankings for the first time since suffering a serious injury at the 2022 French Open.
"That was a performance to match the occasion," Zverev said.
"It was pretty good I have to say. I knew I had to play like this to win. Ugo is an incredible player. Plus him playing in Paris, I think he played even better than he usually does.
"I knew that once the crowd gets involved it would be very, very difficult. I had to take that away early. I did that and I'm happy about it."
The Roland Garros runner-up broke first as he took the opener helped by a number of unforced errors by Humbert.
His performance was just as powerful in the second set as the 27-year-old went on to win the Paris Masters for the first time.
"I want to thank my team. The work we've done over the past two and a half years to be back in this position, everyone had to sacrifice so much. To be able to play on these beautiful courts again," Zverev added.
"There was never a 100% guarantee that I'd be back at this level after Roland Garros two years ago when I basically broke everything in my ankle that's possible.
"To win the title here in Paris means the world to me but I'm sure it also means the world to everybody sitting in my box. They've done so much to help me lift this title."
In winning his seventh ATP Masters 1000 title, Zverev joined Boris Becker as the only German champions in the tournament's history.
He has the most match wins on the ATP Tour this season (66), one ahead of world number one Jannik Sinner.
Swiatek battles past Krejcikova in WTA Finals opener
Iga Swiatek looked rusty on her return after two months out but the world number two rallied for a 4-6, 7-5, 6-2 win over Barbora Krejcikova to kick-start her WTA Finals title defence in Riyadh on Sunday.
Swiatek lost in the U.S. Open quarter-finals in September and was leapfrogged in the world rankings by Aryna Sabalenka after she skipped the WTA Tour's Asian swing due to fatigue.
The 23-year-old, who is looking to reclaim top spot in the Saudi Arabian capital, dropped her serve early and was unable to gain a foothold as Wimbledon champion Krejcikova ran away with the first set.
"It wasn't easy. At the beginning I felt a bit rusty, but I'm happy that I found a way to play a little bit more solid," Swiatek said.
"I didn't feel great (at the beginning). Barbora also used that. The score went her way pretty quickly.
"I knew it was tight even in the first set and I had my chances so I just wanted to use them the next time."
Krejcikova broke twice in the second set after two double faults by an increasingly off colour Swiatek, whose fans at the King Saud University Indoor Arena sensed a big upset and looked to lift the French Open champion.
"I heard it for sure. I missed that. In tough moments today when I heard you guys screaming, it helped me. Thank you for the support. Even though at the beginning my game wasn't nice, you guys still believed."
Swiatek came out swinging from 3-0 down and moved ahead for the first time with a thumping backhand winner, before levelling the match at one set apiece.
She held to love for a 5-0 lead in the decider as Krejcikova struggled with a lower back problem, and withstood a late charge to close out victory.
With Sabalenka defeating Zheng Qinwen on Saturday, Swiatek will need to retain the trophy after winning at least two round- robin matches to have any chance of overtaking the Belarusian and finishing as year-end world number one.
Former U.S. Open champion Coco Gauff then eased past fellow American Jessica Pegula 6-3 6-2 in the other Orange Group match on Sunday.
Elena Rybakina will look to rebound from her opening loss when she plays Zheng on Monday before top seed Sabalenka takes on French Open and Wimbledon finalist Jasmine Paolini in the Purple Group.
