Nagaoka is a city located in the central part of Niigata Prefecture, Japan. It is the second largest city in the prefecture, behind the capital city of Niigata. Nagaoka is located at longitude 138° E and latitude 37° N.
The size of Nagaoka increased on April 1, 2005, when the town of Oguni, the village of Yamakoshi, the town of Nakanoshima, the town of Koshiji, and the town of Mishima in were absorbed into the city of Nagaoka. As of June 1, 2005, the city has an estimated population of 237,115 and a density of 450.88 persons per km². The total area is 525.89 km².
It once again increased on January 1, 2006, when the city of Tochio, the towns of Yoita and Teradomari, and the village of Washima in were absorbed into the city of Nagaoka. As of July 1, 2006, the city has an estimated population of 282,829 and a density of 336.35 persons per km². The total area is 840.88km².
