Masaaki Koyama (小山 正明, Koyama Masaaki, born July 28, 1934 in Akashi, Hyōgo Prefecture, Japan) is a Japanese former professional baseball pitcher in Nippon Professional Baseball (NPB). He played for the Osaka / Hanshin Tigers from 1953 to 1963, the Tokyo / Lotte Orions from 1964 to 1972, and the Taiyo Whales in 1973. He is a member of the Japanese Baseball Hall of Fame.