Stefanos Tsitsipas, who was the runner at this year's Dubai Duty Free Tennis Championship, has won the ATP Finals title.
He came from a set down to beat Dominic Thiem on Sunday night at the O2 Arena in London.
The 21-year-old from Greece took the match in a pulsating final-set tie-break.
Tsitsipas becomes the youngest winner of the season-ending ATP Finals in 18 years.