Which Kurosawa film was made as a Soviet-Japanese co-production?

The Kurosawa film made as a Soviet-Japanese co-production was Dersu Uzala.

Released in 1975, Dersu Uzala was directed and co-written by Akira Kurosawa and produced with the Soviet studio Mosfilm. It adapts Russian explorer Vladimir Arsenyev’s memoir about expeditions through the Russian Far East and his friendship with Dersu, a skilled Goldi hunter and guide. The film was made primarily in the Soviet Union and is spoken in Russian.

The collaboration came at a difficult point in Kurosawa’s career. After Japanese studios became reluctant to finance his projects, Soviet filmmakers offered him the opportunity to work in their country. A contract with Mosfilm was signed in March 1973, with Kurosawa retaining substantial artistic control despite Soviet production requirements and limits on the Japanese crew.

Filming involved severe cold, difficult terrain, illness, and months in the wilderness. The production used 70 mm photography to convey the scale of the taiga and its landscapes. Dersu Uzala received the Academy Award for Best Foreign Language Film at the 48th Academy Awards in 1976. It is sometimes mistaken for Ran or Kagemusha because those are also major late Kurosawa films, but neither was a Soviet-Japanese production.