Iida is a city in Nagano Prefecture, Japan. As of 1 March 2019, Iida had an estimated population of 101,536, and a population density of 154 persons per km2. The total area of the city is 658.66 square kilometres (254.31 sq mi). Iida is an environmental model city , a municipality designated by the Japanese government to be a model for making large cuts in greenhouse gas emissions towards a low-carbon society.

Nagano Prefecture is a landlocked prefecture of Japan located in the Chūbu region of Honshū. Nagano Prefecture has a population of 2,007,682 and has a geographic area of 13,561.56 square kilometres (5,236.15 sq mi). Nagano Prefecture borders Niigata Prefecture to the north, Gunma Prefecture to the northeast, Saitama Prefecture to the east, Yamanashi Prefecture to the southeast, Shizuoka Prefecture and Aichi Prefecture to the south, and Gifu Prefecture and Toyama Prefecture to the west.