Ōsumi (大隅国; -no kuni) was an old province of Japan in the area that is today the eastern part of Kagoshima prefecture. Osumi bordered on Hyuga and Satsuma Provinces.

Osumi's ancient capital was near modern Kokubu. During the Sengoku and Edo periods, Osumi was controlled by the Shimazu clan of neighboring Satsuma, and did not develop a major administrative center.