Mōtsū-ji refers to the Buddhist temple of the Tendai sect in Hiraizumi and to the historic area surrounding it containing the ruins of two older temples, Enryū-ji and Kashō-ji in a Jōdo (Pure Land) garden. The current temple was built in the 18th century and bears no relation to the ancient temples that once stood here. In June 2011, Mōtsū-ji was listed as a UNESCO World Heritage Site as "Historic Monuments and Sites of Hiraizumi".
Previous to the 12th century this area was apparently known as Mōtsū, or Kegosu being an alternate reading of the Chinese characters. These characters mean 'hair' and 'boundary' and refer to the boundary between Japan and the 'hairy people' or Emishi beyond. In other words this was at one time the northern boundary of Japan.
In the mid 12th century Fujiwara no Motohira, the second Northern Fujiwara lord, built a temple here called Enryũ-ji. There is also a possibility that Motohira's father Fujiwara no Kiyohira built an earlier Enryū-ji on this site before he died in 1128. If so, it is supposed that this original temple was consumed by fire soon after its completion in the war of succession between Motohira and his brother Koretsune. The temple built by Motohira around 1150 would then have been a copy of his father's temple.