Aso (阿蘇郡, Aso-gun) is a district located in Kumamoto Prefecture, Japan.
As of the Aso and Yamato mergers (but with 2003 population data), the district has an estimated population of 40,841 and a density of 58.1 persons per square kilometer. The total area is 703.01 km2.
The Aso clan comes from it