Nasu is a town located in Tochigi Prefecture, Japan. As of 1 August 2020, the town had an estimated population of 24,851 in 10,400 households, and a population density of 67 persons per km2. The total area of the town is 372.34 square kilometres (143.76 sq mi).

Tochigi Prefecture is a landlocked prefecture of Japan located in the Kantō region of Honshu. Tochigi Prefecture has a population of 1,897,649 and has a geographic area of 6,408 km². Tochigi Prefecture borders Fukushima Prefecture to the north, Gunma Prefecture to the west, Saitama Prefecture to the south, and Ibaraki Prefecture to the southeast.