Serbia's Hamad Medjedovic became the sixth winner of the Next Gen ATP Finals after a five-set win over France's Arthur Fils.
The 20-year-old world number 111 recovered from letting two match points slip in the fourth set before winning 3-4(6-8) 4-1 4-2 3-4(9-11) 4-1.
The tournament is the season-ending event for the top-ranked male players aged 21 and under.
The event has a best-of-five format with four games winning a set.
Former champions include current top 10 players Carlos Alcaraz, Jannik Sinner and Stefanos Tsitsipas.
This season, Medjedovic reached tour-level semi-finals in Gstaad and Astana and won three ATP Challenger Tour events.