Nishiaizu (西会津町, Nishiaizu-machi) is a town located in Yama District, Fukushima Prefecture, in northern Honshū, Japan. As of September 2014, the town had an estimated population of 6,695 and a population density of 22.5 persons per km². Approximately 66% of the population is over the age of 65. The total area was 298.13 km².