The Ōminato Guard District was the major navy base for the Imperial Japanese Navy in northern Honshu before and during World War II. Located in Mutsu Bay at the present-day city of Mutsu, Aomori Prefecture, the Ōminato Guard District was responsible for control of the strategic Tsugaru Strait between Honshu and Hokkaidō and for patrols along the Hokkaidō, Karafuto and Kurile Islands coastlines.

Mutsu is a city located in Aomori Prefecture, Japan. As of 31 January 2023, the city had an estimated population of 53,804 in 28553, and a population density of 62 persons per km2. The total area of the city is 864.12 square kilometers (333.64 sq mi), making it the largest municipality in Aomori Prefecture in terms of area.