Kōshū is a city located in Yamanashi Prefecture, Japan. As of 1 June 2019, the city had an estimated population of 31,526 in 13,147 households, and a population density of 120 persons per km². The total area of the city is 264.11 square kilometres. The city is the home of the indigenous Koshu grape and is synonymous with viticulture and wine production in Japan.