Tagajō is a city located in Miyagi Prefecture, Japan. As of 1 June 2020, the city had an estimated population of 62,869 in 27,869 households, and a population density of 3,200 people per km². The total area of the city is 19.64 square kilometres (7.58 sq mi). The city was named after Taga Castle, the capital of Mutsu Province from the Nara period.

Miyagi Prefecture is a prefecture of Japan located in the Tōhoku region of Honshu. Miyagi Prefecture has a population of 2,265,724 and has a geographic area of 7,282 km2 (2,812 sq mi). Miyagi Prefecture borders Iwate Prefecture to the north, Akita Prefecture to the northwest, Yamagata Prefecture to the west, and Fukushima Prefecture to the south.