Kiyotsugu Hirayama (平山 清次, Hirayama Kiyotsugu, October 3, 1874 – April 8, 1943) was a Japanese astronomer, best known for his discovery that many asteroid orbits were more similar to one another than chance would allow, leading to the concept of asteroid families, now called "Hirayama families" in his honour.
[1] Hirayama studied astronomy at Imperial University of Tokyo and graduated in 1897.
He taught astronomy in the engineering school of the General Staff Office of the Japanese Army between 1897 and 1901.
From 1906 to 1907 Hirayama was a member of the Committee that determined the latitude border at Sakhalin after the Russo–Japanese War.
In 1911 he received a doctoral degree "with several papers about latitude variation".