Alexander Zverev captured his second ATP Finals title after producing a brilliant performance to defeat world number two Daniil Medvedev 6-4, 6-4 in Sunday's final in Turin.
Zverev, the Olympic singles gold medallist in Tokyo, won his tour-leading sixth trophy of the season and ended a run of five straight losses to defending champion Medvedev.
The German third seed broke once in each set as he swept US Open winner Medvedev aside in 75 minutes to add to the season-ending crown he won in 2018.
"It was great, I won the ATP Finals against someone I'd lost to five times in a row so I had to play one of my best matches," Zverev said.
"I'm happy with that and ready to go on holidays with this win now."
Zverev will skip the Davis Cup finals to be played in Madrid, Turin and Innsbruck from November 25 to December 5.
"There's no better way to end the season than winning here so obviously I'm incredibly happy. But I'm now very much looking forward to next year already," he said.
"It's very special, I'm super thrilled and super happy right now."
The ATP Finals, this year missing Roger Federer and Rafael Nadal, have proved the breakout stage for the new generation of tennis, with the Grand Slams still largely beyond their reach.
This first final since the tournament's relocation from London was also the first to feature two players aged 25 or younger since 2005.
Zverev, conqueror of top-ranked Novak Djokovic in Saturday's semi-finals, landed the first blow against Medvedev by breaking for a 2-1 lead in the first set.
The Russian avoided further damage by saving another break point in game five but Zverev barely gave Medvedev a sniff, winning 20 of 25 points on serve to take the opener.
Zverev broke again at the start of the second set and held serve throughout, not offering a single break point and sealing victory with an ace out wide to avenge his round-robin loss to Medvedev.
An ATP-best 59th win of the season made Zverev the fourth player in tournament history to earn semi-final and final victories over the top-two ranked players, and first since Andre Agassi in 1990.
Zverev halted Djokovic's bid to match Federer with a record-equalling sixth ATP Finals title. He also stopped Medvedev from becoming the first player to retain the trophy since Djokovic won it four times in a row between 2012 and 2015.
"It's been a great season. It's not easy to get to the Masters final and for myself I was really happy to be here," Medvedev said.
"Hopefully I'm going to be a part of many of these tournaments and can try to win one more time."
It was the third meeting in little over two weeks for Zverev and Medvedev, who beat the German in the semi-finals of the Paris Masters at the start of the month.
Zverev turned the tables on Medvedev to claim his 19th career title, but the 24-year-old is still searching for an elusive Grand Slam triumph after finishing runner-up to Dominic Thiem at the 2020 US Open.
"I've kind of succeeded on every single level. There only one thing missing, so I hope I can do that next year," said Zverev.
Medvedev, who shattered Djokovic's dreams of a calendar Grand Slam in New York, believes Zverev can take that next step.
"There are a lot of great players who don't have a Grand Slam title," Medvedev said.
"You never know where your career is going to go. Some players start to play worse, somebody gets injured, somebody wins 20 Grand Slams.
"Sascha (Zverev) is a great player who is capable of beating anybody, so he definitely can win a Grand Slam, but he's not the only one and that's where it gets tough.
"Is he capable? Yes. Is he going to do it? We never know."