World Championship bronze medallist Lee Hyun-il claimed the Badminton World Federation (BWF) US Open title after easing past Japan's Kanta Tsuneyama in Los Angeles.
After a tight first game the 36-year-old South Korean eased home in the second in the Californian city, coming through 24-22, 21-8.
Lee won his world bronze medal in Madrid in 2006 and has twice come fourth at Olympic Games - losing bronze medal matches at both Beijing 2008 and London 2012.
He has also won two Asian Games gold medals in team competitions.
In the women's competition Ayumi Mine won an all Japanese final after outlasting compatriot Saena Kawakami.
Mine came from behind to triumph 16-21, 21-11, 21-15 at the Los Angeles Badminton Club in the 2024 Summer Olympic bid city.
Doubles finals were also contested at the US Open, a BWF Grand Prix Gold level event.
Denmark's London 2012 silver medallists Mathias Boe and Carsten Mogensen claimed the men's doubles title, seeing off the challenge of Japan's Takuro Hoki and Yugo Kobayashi 21-11, 22-20.
An all Japanese women's doubles final went the way of Shiho Tanaka and Koharu Yonemoto, who were 20-22, 21-15, 21-19 winners over Mayu Matsumoto and Wakana Nagahara.
Japan also enjoyed mixed doubles success as Yugo Kobayashi and Wakana Nagahara saw off Poland's 2012 European champions Robert Mateusiak and Nadiezda Zieba, 21-16, 21-18.