Oshika (牡鹿郡, Oshika-gun) is a rural district located in Miyagi Prefecture, in the Tōhoku region of northern Japan.
Most of the city of Ishinomaki was formerly within the district. From 2006, the district has consisted only of the town of Onagawa. As of 2021, the district has an estimated population of 5,636 and a population density of 86.2 persons per km2. The total area was 65.35 km2.