Iwadeyama Castle was a castle in Ōsaki, Miyagi Prefecture, Japan. After serving Hideyoshi for a time, Date Masamune was given Iwatesawa castle and the surrounding lands as his home domain. Masamune moved there in 1591, rebuilt the castle, renamed it Iwadeyama, and encouraged the growth of a town at its base. Masamune stayed at Iwadeyama for 13 years and turned the region into a major political and economic center.