The site on which Bunratty Castle stands was in origin a Viking Trading Camp in 970. The present structure is the last of four castles to be built on the site. Robert De Muscegros, a Norman, built the first defensive fortress (an earthen mound with a strong wooden tower on top) in 1250. His lands were later granted to Thomas De Clare who built the first stone castle on the site. About this time Bunratty became a large town of 1,000 inhabitants.

In 1318 Richard De Clare, son of Thomas was killed in a battle between the Irish and the Normans. His followers were completed routed and the castle and town were completely destroyed.