Iwakuni Castle is a castle in Iwakuni, Yamaguchi, Japan.
This castle was constructed by Kikkawa Hiroie from 1601 to 1608 as his own castle. Kikkawa was a retainer of a vassal of the Shogun under the Mōri clan. However, this castle was dismantled as per the Ikkoku-ichijo (一國一城, literally, "One Castle Per Province") order established by the Tokugawa Shogunate in 1615. The famous Kintai Bridge was originally a bridge to the main gate of the castle. After the destruction of the castle, Kikkawa used a part of the old castle as his residential office. The Kikkawa clan held this castle and Iwakuni Han, which was assessed at 30,000 (later 60,000) koku.
A replica of the castle tower stands high on a hill above the Nishiki River and the Kintai Bridge in the city of Iwakuni, Yamaguchi Prefecture. Iwakuni Castle was selected to be one of the 100 Great Castles of Japan by the Japan Castle Foundation in 2006.