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 (60.24 sq mi). Karuizawa, one of the oldest and most famous summer resorts in Japan, has been visited by many people from around the world since the 19th century.

A resort town, resort city or resort destination is an urban area where tourism or vacationing is the primary component of the local culture and economy. A typical resort town has one or more actual resorts in the surrounding area. Sometimes the term resort town is used simply for a locale popular among tourists. One task force in British Columbia used the definition of an incorporated or unincorporated contiguous area where the ratio of transient rooms, measured in bed units, is greater than 60% of the permanent population.