This castle is situated on the shores of Donegal Bay about three miles from the town of Ballyshannon, in the Barony of Kilbarron, County Donegal.

The name Cill-Barrainn signifies “the Church of St. Barrfhionn.”

The fortress was built on a high and nearly insulated cliff, and from its romantic and wild situation a tradition falsely sprang up that it had been the stronghold of freebooters. The promontory is nearly circular in form and rises a hundred feet above the sea, along the edge of which a wall was built, while on the landward side a thick wall, the whole width of the neck protected this direction from attack.

To the north of the small open courtyard thus enclosed was the keep, and here are traces of a subterranean passage, now filled up, which was used for “distillery purposes” in the eighteenth century.

The remains of two chambers at the cliff side seem older than the other buildings. The sea wall is pierced by an oblong passage with a small square mouth popularly known as “the murdering-hole.”

The castle was probably erected in the thirteenth or fourteenth century by the O’Sgingins, who were ollaves or historians to the great O’Donnells.

In 1391 the Four Masters tell us it was demolished by Donnell, the son of Murtough (O’Conor of Sligo).

The last of the O’Sgingins to be chief historian to O’Donnell in the fourteenth century had no son, and only one beautiful daughter, with whom Cormac O’Cleary, who was on a visit to the Abbey of Assaroe, from Galway, fell in love.

O’Sgingin gave his consent to the marriage, and instead of the wedding gift which it was usual for the bridegroom to present to his wife’s father, O’Sgingin asked that if a son were born of the marriage he should be brought up with a knowledge of literature and history.

Hence Kilbarron passed into the O’Cleary family, and this great race of historians occupied it for several centuries.

It is likely Cormac O’Cleary re-edified it, but the “stone houses,” of which the building is recorded, were erected by Diarmaid, one of the celebrated sons of Tadhg Cam (or The Stooped) O’Cleary.

The fortunes of the Ollaves of Tirconnell began to wane with that of their patrons, the O’Donnells, although the last O’Cleary to hold lands was not dispossessed until 1632, yet many of their possessions were lost to them at the flight of the Northern Earls in 1607. Most of the estate passed to Lord Folliott and the Bishop of Raphoe.