Dufferin (from Irish [A]n Duibhthrian, meaning 'the black third'[2]) is a historic barony in County Down, Northern Ireland.

[3] It is on the southern half of the west shore of Strangford Lough, and is bordered by three other baronies: Castlereagh Lower to the north; Castlereagh Upper to the west; and Lecale Lower to the south.

[3] Dufferin, along with the barony of Kinelarty and part of Castlereagh was at one time part of the territory of the Cenél Foghartaigh (Kinelarty), ruled by the Mac Artáin (MacCartan) sept.[4][5] The Ó Labhradha (Lowry, Lavery) sept are also noted in Dufferin.

[5][6] In the reign of Henry VIII the White family, who were originally from Flemington in County Meath, became Lords of the Manor of Dufferin.

[7] The Whites, although they were driven away for a time due to local disturbances, owned Dufferin until 1610, when they sold the barony to James Hamilton, 1st Viscount Claneboye.