Miyao Castle (宮尾城, miyao-jō) was a fortification built on the island of Itsukushima (also known as Miyajima) during the Sengoku Period in Japan.

[1] Built by Mōri Motonari, Miyao Castle was part of a greater plan to bait and trap his enemy, Sue Harukata, which culminated in the Battle of Miyajima in 1555.

[3] As site for Miyao Castle, Mōri Motonari selected a 30-meter hill called Yougai-san (要害山) in the northwest corner of the island, near the main shrine and overlooking the channel between Miyajima and the mainland.

Stone walls had to be built in order to buttress the weakly tamped earthen foundation which, without support, would have easily collapsed.

[3] Although Motonari's forces were heavily outnumbered, he knew the land and the castle's weaknesses, and thus had the tactical advantage as well as the element of surprise.

Of further consideration is the fact that Miyao Castle was built on sacred ground, and the ensuing battle was itself an act of desecration in a place where neither birth nor death are supposed to occur.