Niigata Prefecture is a prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,131,009 and is the fifth-largest prefecture of Japan by geographic area at 12,584.18 km². Niigata Prefecture borders Toyama Prefecture and Nagano Prefecture to the southwest, Gunma Prefecture to the south, Fukushima Prefecture to …Niigata Prefecture is a prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,131,009 and is the fifth-largest prefecture of Japan by geographic area at 12,584.18 km². Niigata Prefecture borders Toyama Prefecture and Nagano Prefecture to the southwest, Gunma Prefecture to the south, Fukushima Prefecture to the east, and Yamagata Prefecture to the northeast.