Amakusa (天草郡, Amakusa-gun) is a district located in Kumamoto Prefecture, Japan.
Following the March 27, 2006 Amakusa merger the district consists of the single town of Reihoku. After the merger, the district has an estimated population of 9,105 and a density of 135.77 persons per km2. The total area is 67.06 km2.