Pathunyu "Guy" Yimsomruay (born July 6, 1979) is a Thai former swimmer, who specialized in backstroke and in individual medley events. He is a single-time Olympian (2000), and a four-time medalist at the Southeast Asian Games (1997, 1999, 2001, and 2003). While studying in the United States, Yimsomruay earned four All-American and five All-ACC honors for the Virginia Cavaliers.