Koga is a Japanese surname. Notable people with the surname include:

• Harue Koga, Japanese painter active in the Taishō period
• Hiroyasu Koga, Yukio Mishima's kaishakunin
• Issei Koga, for Democratic Party of Japan
• Junya Koga, Japanese swimmer
• Kazunari Koga, Japanese footballer
• {{Nihongo|Koichiro Koga|古賀 幸一郎||born 1984}}, Japanese volleyball player
• Makoto Koga, Japanese Liberal Democratic Party politician
• Mary Koga (1920-2001), Japanese-American photographer and social worker in Chicago
• Masahiro Koga, Japanese footballer
• Masao Koga, was a Japanese composer, guitarist and pop musician
• Mineichi Koga (1885–1944), Fleet Admiral during World War II
• Mitsuki Koga, actor in martial arts films
• Sarina Koga, Japanese volleyball player
• Satoshi Koga, Japanese footballer
• Seiji Koga, Japanese footballer
• Tadayoshi Koga, pilot of the Akutan Zero in World War II
• {{Nihongo|Taichirō Koga|古賀 太一郎||born 1989}}, Japanese volleyball player
• Takuma Koga, Japanese footballer
• Toshihiko Koga, a judo world champion
• Yukiko Koga, anthropologist
• Yun Kōga (born 1965), Japanese manga artist

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