Dunduff Castle is a restored stair-tower in South Ayrshire, Scotland, built on the hillside of Brown Carrick Hills above the Drumbane Burn, and overlooking the sea above the village of Dunure.

[4] Lying to the east of Dunduff Farm on a rocky knoll, this tower castle was built to an L-shaped plan, with a square three floored stair-tower[5] in the re-entrant angle on the south.

Window and door features of the original ruin suggest construction in the late 16th and early 17th centuries.

In 1891 the Rev R Lawson in his book, Places of Interest about Maybole with Sketches of Persons of Interest,[18] states:- On the hill side above stand the ruins of the unfinished castle of Dunduff a local illustration of that searching question of our Lord's—" Which of you, intending to build a tower, sitteth not down first and counteth the cost, whether he have sufficient to finish it Lest haply, after he hath laid the foundation, and is not able to finish it, all that behold it begin to mock him, saying, This man began to build and was not able to finish.

[25] The Laird of Bargany then had an unsuccessful property dispute with the earl over the lands of Newark,[28] which resulted in a fourth member joining the group and an attempt on the life of Culzean being made.

[29] On 1 January 1598 the earl dined at supper with Sir Thomas Nasmyth at Maybole and the plotters and their servants lay in wait, however despite eight shots being fired at him, the earl escaped unharmed, having run away through the streets of Maybole with the benefit of a dark and murky night for concealment.

[28] The result of this incident for the Laird of Dunduff was that he was held briefly in Edinburgh Castle and was then banished from Scotland, England, Ireland and all the Isles and fined 1000 merks.

[29][30] This sentence was either evaded or not enforced and upon his return the laird and the earl settled their disagreements and became friends; he died in 1609.

In 1668, it is recorded that the John, the fifth (and last) Stewart Laird of Dunduff and his brother William were prevented, being opposed to Oliver Cromwell and supporting the crown, from renewing the covenant and shortly after the property was sold and passed into the hands of the Whiteford family.

These lands were in County Donegal known as Coolaghy in the Barony of Raphoe, known as Fort Dunduff and later as the Manor of Mount-Stewart.

[25] Mount-Stewart in Donegal should not be confused with Mount Stewart in County Down, Northern Ireland, which was latterly the home of the Vane-Tempest-Stewart family, Marquesses of Londonderry.

The mill was powered by one of the burns running off the Brown Carrick Hill, but its exact location is unknown.

[40] Smith and others record an Iron Age fort or motte with this name on a separate rocky knoll about 170 metres (560 feet) west of the castle.

[42] The exact location has been lost, but in 1655 a Dunduff Creek is recorded as being in use as a small harbour between Dunure and the Heads of Ayr.

[42] To the west of the castle, just beyond Dunduff Farm, are the rectangular shaped ruins of the pre-reformation church, dedicated to St Brigid, the Irish Saint from Kildare, who lived c.453–525 Other Ayrshire dedications included Giffen and Trearne, Irvine, Sundrum, Ardrossan, West Kilbride and South Kilbride near Stewarton.

Kirkebride at Larges (sic) had belonged to the Cistercian foundation of St Mary of North Berwick, together with 52 acres (21 hectares) of land and a salt pan.