1942 GA. Discovered 1942 Apr. 6 by K. Reinmuth at Heidelberg.

Named in memory of Issei Yamamoto (1889–1959), professor of astronomy at Kyoto University, director of the Kwasan Observatory, and first president of the IAU commission on the zodiacal light. The most well-known popularizer of astronomy in Japan, he founded the Oriental Astronomical Association in 1920 and was a source of encouragement for many amateur astronomers in Japan. (M 6648)

Name proposed by S. Nakano, who determined the orbit for this planet.

Yamamoto is also honored by a lunar crater.