Valentin Vacherot became Monaco's first ATP Tour singles champion and the lowest-ranked player in history to win a Masters 1000 event.
He beat his cousin Arthur Rinderknech in Shanghai, coming from a set down for the sixth time in the tournament to win 4-6 6-3 6-3.
Vacherot previously beat four-time Shanghai champion Novak Djokovic in the semi-finals.
Rinderknech struck 12 winners and committed just two unforced errors on his way to winning the opening set.
However, Vacherot broke his opponent in consecutive games from 3-3 in the second set to lead by a break in the third.
Author's summary: Vacherot wins Shanghai Masters title.