First recorded in 1440 when it was seized by an O’Donnell son before being returned to the O’Boyle clan, this stronghold served as the O’Boyles’ principal residence for over a century. The castle witnessed significant conflict during the Nine Years’ War, notably when Red Hugh O’Donnell expelled English forces from its walls in 1592, though it would ultimately fall to colonial administration when the lands were granted to Patrick Vans in 1610.

Following the Plantation of Ulster, Sir Paul Gore attempted to resurrect the site in 1611, constructing what was described as ‘a fair stone house’ from the castle’s ruins, though he was forced to surrender it to George Murrey shortly after. By 1622, official records paint a picture of decay, describing ‘the ruinous castle of Ballyboyle; to which is adjoined the walls of a house, built about 7ft high by Sir Paul Gore’. The Civil Survey of 1654 to 1656 mentions only ‘ye old walls of ye Castle called Balliweill’, suggesting further deterioration during the Confederate Wars.

Today, visitors to the site will find no trace of the original castle itself, though the ivy-clad ruins of a subcircular corner tower and sections of wall from what was likely a defensive bawn still cling to the cliff edge. The tower, which has partially collapsed since the 1940s, originally featured four gun loops at ground level and was topped with a mortared, corbelled vault. Foundation traces can be followed eastward along the cliff to a ruined gate lodge, whilst approximately 2.7 metres of the northwest wall survives to a height of about one metre, offering tantalising glimpses of this once-formidable fortress that commanded the Donegal coastline.