Kumagaya (熊谷市 Kumagaya-shi?) is a city located in Saitama Prefecture, Japan. As of 2010, the city has an estimated population of 203,089 (9th in Saitama) and a population density of 1,270 persons per km². The total area is 159.88 km². The city is one of the biggest in northern Saitama Prefecture. It is the administrative, business and commercial centre in northern Saitama Prefecture. Eight national highways and three railway lines serve the city. While many people commute towards south Tokyo, its daytime population is larger than the night population thanks to commuters from surrounding towns.