Tsuyoshi Ihara (いはら つよし, Ihara Tsuyoshi, Korean: 윤유구; born November 6, 1963) is a Japanese actor, martial artist, and writer of Korean descent.

Ihara is a Japanese person of Korean descent, born on November 6, 1963, in Kitakyūshū as Yun Yu-gu (윤유구; 尹惟久) and who grew up in Ikuno-ku, Osaka.

Ihara joined the Japan Action Enterprise, a theater troupe founded by Sonny Chiba, after leaving high school.

Soon after, he began to work in numerous feature films and television dramas, including the 1996 NHK series Futarikko.

In 2006, Ihara appeared as the Baron Takeichi Nishi in Clint Eastwood's critically acclaimed Academy Award-winning film Letters from Iwo Jima, introducing him to a wider international audience.