The castle was built by the O’Heyne clan, who held these lands for centuries as lords under the O’Kellys of Uí Maine. Its strategic position allowed the O’Heynes to control both the river crossing and the coastal approach to their territory, making it an important defensive stronghold in medieval Galway.

The castle itself is a typical example of Irish tower house architecture from this period; a rectangular stone structure rising four storeys high with thick walls designed to withstand siege. Though now roofless and partially ruined, the remaining walls show evidence of its former grandeur, including the remains of window openings, murder holes, and a spiral staircase built into the thickness of the walls. The ground floor, as was common in such towers, likely served as storage, whilst the upper floors contained the living quarters and great hall where the O’Heyne chieftains would have entertained guests and conducted their affairs.

Today, Dunkellin Castle stands as a silent witness to the tumultuous history of County Galway. The castle passed through various hands over the centuries, eventually falling into ruin after the Cromwellian conquest of Ireland in the 1650s. Despite its current state, the tower remains an impressive sight, particularly when viewed from the nearby N67 road. The surrounding landscape, with its mix of farmland and coastal views, has changed little since the castle’s heyday, offering visitors a glimpse into what life might have been like for the Gaelic lords who once ruled this corner of Ireland.