Karuizawa is a resort town located in Nagano Prefecture, Japan. As of 1 October 2016, the town had an estimated population of 20,323 in 9897 households, and a population density of 130 persons per km2. The total area of the town is 156.03 km2. Karuizawa is one of the oldest and most famous summer resorts in Japan, visited by many people from different countries since the 19th century.