Ryōhei Koiso (小磯 良平 Koiso Ryōhei?) (July 25, 1903 - December 16, 1988) was a Japanese artist. He graduated from the Tokyo University of the Arts western art department in 1927 and had a successful career from early on. During World War II he was often commissioned paintings depicting Japanese military scenes, such as the signing of the British surrender of Singapore, and Japanese infantrymen making their way through high grass fields in Malaysia. He returned to mainstream painting following the war, and painted until his death.