Minamioguni (南小国町, Minamioguni-machi) is a town located in Aso District, Kumamoto Prefecture, Japan.

Minamiogun is located in a plateau area at an altitude of 430 to 945 meters outside the northern outer rim of Mount Aso.

Minamioguni has a mayor-council form of government with a directly elected mayor and a unicameral town council of 12 members.

Minamioguni, collectively with the other municipalities of Aso District contributes one member to the Kumamoto Prefectural Assembly.

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