Koshu Tani (? ??, Tani Koshu, born March 30, 1951 in Itami, Hyogo Prefecture, Japan) is an award-winning Japanese science fiction writer.
He graduated from the Osaka Institute of Technology, and worked as a volunteer in Nepal and the Philippines.
He made his professional debut with the story 137th Mobile Brigade in 1979 while still in Nepal.
He is known mostly for his hard science fiction works, for which he won the Seiun Award three times (twice for Best Novel, and once for Best Short Story), and the Nitta Jiro Culture Award once.
He is a member of the Mystery Writers of Japan, the Science Fiction and Fantasy Writers of Japan, the Space Authors Club, and an associate member of the Hard SF Laboratory.
Tani currently lives in Komatsu in Ishikawa Prefecture.