Alexander Zverev continued his dominant form since the summer, beating Frances Tiafoe 7-5 6-4 in the Vienna Open final.
Germany's Zverev, 24, edged the 23-year-old American qualifier in two tight sets to claim his fifth tour level title this season.
The pair traded breaks before Olympic champion Zverev broke at the end of the first set to lead.
He pressured Tiafoe throughout the second set, breaking to love to win.
Zverev has won all five finals he has contested this season, also winning titles in Acapulco, the Madrid and Cincinnati Masters, and Olympic gold in Tokyo, losing just two matches since the Wimbledon fourth round.
The German has already qualified for the ATP Tour Finals, which he won in 2018, to be held in Turin.
In early October, the ATP announced it was investigating claims that Zverev was violent towards a former girlfriend. He denies the allegations.
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Elsewhere, Croatia's former US Open champion Marin Cilic won his first hard court title since 2016, beating America's Taylor Fritz 7-6 (7-3) 4-6 6-4 in the St. Petersburg final.
Donna Vekic, another Croat, beat Danish teenager Clara Tauson 7-6 (7-3) 6-2 at the Courmayeur Ladies Open to win her first title in more than four years.
At her home tournament in Romania, former world number one Simona Halep lost to Estonia's Anett Kontaveit 6-2 6-3, at the Transylvania Open.
The win, together with her Moscow title last week, secures a spot for Kontaveit at the WTA Finals to be held in Guadalajara, Mexico from on 10 November.
BBC