Karuizawa(軽井沢町,Karuizawa-machi) is a town in Kitasaku District, Nagano Prefecture, Japan.

As of February 2016, the town has an estimated population of 19,769 and has a total area of 156.05 square kilometres (60.25 sq mi).

At an elevation of 1,000 m (3,281 ft) and a temperate summer climate, Karuizawa is a popular year round resort offering many outdoor sport, hot spring and recreational activities. Convenient road and rail access from central Tokyo, has ensured Karuizawa's popularity as a location for second homes and resort hotels since the Meiji era. The town is known for its historic shopping street known as "Ginza dōri" or "Kyū-dō" (Ginza Street, or the Old Road) and association with both Japanese royalty and visitors such as John Lennon and Yoko Ono. Karuizawa hosted equestrian events in the 1964 Summer Olympics as well as curling in the 1998 Winter Olympics. To date, it is the only city in the world to have hosted both Summer and Winter Olympic events.