Valentin Vacherot became Monaco's first ATP Tour singles champion and the lowest-ranked player in history to win a Masters 1000 event.
He defeated his cousin Arthur Rinderknech in Shanghai, coming from a set down to win 4-6 6-3 6-3.
Vacherot, ranked 204 in the world, had previously beaten four-time Shanghai champion Novak Djokovic in the semi-finals.
Rinderknech won the opening set, striking 12 winners and committing just two unforced errors, but Vacherot broke his opponent in consecutive games to lead by a break in the third.
He came from a set down for the sixth time in the tournament to win.
Author's summary: Vacherot wins Shanghai Masters title.