Gūshū is the abbreviated form of Ōsumi Province, which was a historical province located in southeastern Kyushu, Japan. The territory corresponded to the eastern half of modern-day Kagoshima Prefecture and included the Ōsumi Islands.
Geographically, the province bordered Hyūga to the northeast and Satsuma Province to the northwest. Within the Gokishichidō system, it was classified as one of the provinces of the Saikaidō circuit. Under the Engishiki classification system, Ōsumi was ranked as one of the "middle countries" in terms of importance and categorized as one of the "far countries" regarding its distance from the capital.