Iwaki (いわき市 Iwaki-shi) is a city located in Fukushima Prefecture, Japan. As of 1 August 2023, Iwaki had a population of 322,019 in 143,500 households and a population density of 261 persons per km². The city's total area is 1,232.02 square kilometres (475.69 sq mi), making it the largest city in the prefecture and the 10th largest city in Japan (2010) in terms of area. Iwaki is a designated core city and is also one of the growing numbers of cities written in hiragana. Iwaki City started by merging 14 smaller municipalities on 1 October 1966. Iwaki hosts the Taira Tanabata Festival from 6–8 August every year.