Aga is a town located in Niigata Prefecture, Japan. As of 30 November 2020, the town had an estimated population of 10,386 in 4490 households, and a population density of 11 persons per km2. The total area of the town is 952.89 square kilometres (367.91 sq mi).

Niigata Prefecture is a prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,131,009 and is the fifth-largest prefecture of Japan by geographic area at 12,584.18 km2 (4,858.78 sq mi). Niigata Prefecture borders Toyama Prefecture and Nagano Prefecture to the southwest, Gunma Prefecture to the south, Fukushima Prefecture to the east, and Yamagata Prefecture to the northeast.