Built of local flagstone, this 8.9-metre diameter fortress likely dates to the 14th or 15th century when it was constructed by the O’Connor family. The castle’s ownership shifted through several prominent Irish families over the centuries, including the O’Briens and the MacClancys, who served as brehons (traditional lawyers) to the O’Briens of Thomond. Local tradition holds that Boetius MacClancy presided over trials here that condemned Spanish Armada survivors to death, adding a dark chapter to the castle’s already turbulent history.

The tower’s defensive architecture reveals sophisticated medieval engineering, with walls nearly two metres thick housing an intricate network of chambers and passages. Each of the four floors served distinct purposes; the ground floor featured loop embrasures and storage areas, whilst upper levels contained living quarters with fireplaces, garderobes, and defensive features. The third floor showcases particularly fine details, including double-light cusped ogee-headed windows and an elaborate conical oak roof with a central king-post. Intramural staircases wind through the walls, connecting the main chambers to smaller defensive spaces, including what appears to have been a prison cell that could be bolted from the outside, and a separate lock-up chamber that could be secured from within during attacks.

Following the 1641 rebellion, the castle passed through various hands, eventually coming into the possession of the Gore family by 1719, who later granted it to John Vandeleur of Kilrush. The castle underwent repairs in the 1830s under Counsellor Gore’s direction, helping preserve this impressive example of Irish tower house architecture. Today, protected under a preservation order since 1972, Doonagore Castle remains surrounded by remnants of its original bawn wall, offering visitors a tangible connection to centuries of Irish history, from medieval clan conflicts to the tragedy of the Spanish Armada.