Asaka, city, southeastern Saitama ken (prefecture), east-central Honshu, Japan. It lies along the Kurume River just northwest of Tokyo.
It was a post town known as Hizaori during the Edo (Tokugawa) period (1603–1867). Its name was changed to Asaka in 1932. The city has been a centre of the copper-rolling industry since the late 19th century. It is connected by rail and highway with Tokyo and is now a residential suburb of the Tokyo-Yokohama metropolitan area. Asaka is also the site of a large military base. Pop. (2010) 129,691; (2015) 136,299.