The holotype (UHR 6590, University of Hokkaidō Registration) was discovered in November 1934 during the construction of a hospital for the Kawakami colliery of the Mitsui Mining Company on Karafuto Prefecture (now Sinegorsk, Sakhalin, Russia), and additional material belonging to the specimen was recovered in the summer of 1937. The type species Nipponosaurus sachalinensis was in 1936 named and described by Professor Takumi Nagao of the Imperial University of Hokkaido. The generic name refers to Nippon, the Japanese name of Japan; it was the first dinosaur named based on a find made on Japanese territory — though South Sakhalin was annexed by the Soviet Union in 1945. The specific name refers to Sakhalin. In 1938 Nagao dedicated a second article to the species.