Iwanuma is a city located in Miyagi Prefecture, Japan. As of 31 March 2020, the city had an estimated population of 43,946 in 18,062 households, and a population density of 730 persons per km². The total area of the city is 60.45 square kilometres (23.34 sq mi). Iwanuma is at the convergence of two ancient roads, the Tōkaidō and the Rikuzen-Hama Kaidō.