Aso (阿蘇市, Aso-shi) is a city located in Kumamoto Prefecture, Japan.

The name appears in the Nihon Shoki as "Aso-no-kuni" and was ruled by the Aso clan from ancient times.

After the Meiji restoration, the villages of Uchimaki, Kurokawa, Eisui, Ogaishi, Yamada, Miyaji, Furushiro, Nakadori, Sakanashi and Namino were established in Aso District with the creation of the modern municipalities system on April 1, 1889.

Aso has a mayor-council form of government with a directly elected mayor and a unicameral city council of 18 members.

In terms of national politics, the city is part of the Kumamoto 3rd district of the lower house of the Diet of Japan.