France's Arthur Fils came back from a match point down to win the Japan Open with a 5-7, 7-6 (8/6), 6-3 victory over countryman Ugo Humbert on Tuesday.
Fils, the world number 24, came back from the brink to edge his Paris Olympics doubles partner in 3hr 4min in Tokyo.
It gave the 20-year-old Fils his third career title and second this year, following his success in Hamburg.
Humbert, the world number 19, lost a final for the first time in his career, having won the previous six.
He was bidding to become the first player in ATP tour history to win his first seven finals.
Fils became the youngest champion in Tokyo in over 40 years and he had to do it the hard way when he faced match point in the second-set tiebreak.
He survived it to level the match before breaking Humbert to for a 5-3 lead in the final set that left him serving for the championship.
He clinched the victory on his first match point with an ace down the centre before collapsing to the ground.
Fils knocked out top seed and US Open finalist Taylor Fritz in the first round.
He also came through gruelling matches against defending champion Ben Shelton and No 6 seed Holger Rune to reach the final.
It was the first all-French final on the ATP tour in four years.