Site of Ringdufferin Castle, near Ringdufferin House, 35 Ringdufferin Road, Ringdufferin, Near Killyleagh, Co. Down, BT30 9PH

Site of a castle or tower house built around 1590-1600, of which no visible trace now remains. The site lies approximately 2.5 miles north-northeast of Killyleagh, amidst well-wooded grounds overlooking the east coast of Strangford Lough. It is now occupied by Ringdufferin House, a large gentleman's residence dating mainly from the late 18th century, together with adjacent rubble-built outbuildings of probably contemporary date.

The earliest reference to a structure at this location appears in State Papers dating from around 1602, which records a castle built by John White "on a neck of land", leased to him by Sir Ralph Lane, and called Randuffren. The precise position of the original castle remains uncertain. While ordnance survey maps from 1859 onwards have generally favoured a location close to the present house, the existence of an area called Castle Island on the isthmus immediately to the south may indicate the castle actually stood there instead. It is not known whether Ringdufferin House occupies the site of the original castle or incorporates any of its fabric, although no documentary or physical evidence currently suggests this to be the case.

In 1636 Alexander Baillie of Innishargy (near Kircubbin) received the lands of Ringdufferin on mortgage from the 1st Viscount Clandeboy, becoming the absolute owner in 1674. His descendants retained possession for the following two centuries, during which period Ringdufferin House and its associated buildings assumed much of their present form. Whether the Baillies made use of the castle or incorporated it into a later dwelling is unknown. It is probable that the original castle was dismantled and its stone reused in later buildings.