Teenager Joao Fonseca beat American Learner Tien to be crowned the second- youngest winner of the Next Gen ATP Finals title after Jannick Sinner in 2019.
The 18-year-old Brazilian, who was the youngest player in this year's competition and lowest ranked, overcame Tien 2-4 4-3 (10-8) 4-0 4-2 in Jeddah.
Fonseca won all five of his matches at the season-ending tournament for the top-ranked male players aged 21 and under.
The pair also met in the group stage on Thursday, with Fonseca, ranked 145th in the world, again coming out on top against his 19-year-old opponent.