Rathdown (Irish: Ráth an Dúin) is the south-easternmost barony in County Dublin, Ireland.[1][2] It gives its name to the county of Dún Laoghaire–Rathdown. Before County Wicklow was shired in 1606, Rathdown extended further south: it was named after a medieval settlement which grew up around Rathdown Castle, at a site subsequently deserted and now in County Wicklow in the townland of Rathdown Upper, north of Greystones.[3][4] The Wicklow barony of Rathdown corresponds to the portion transferred to the new county; although both divisions were originally classed as "half baronies", in the nineteenth century the distinction between a barony and a half barony was obsolete.
Other settlements in the barony include Dundrum.[1] "Little Bray", the part of the township of Bray north of the River Bray, was transferred from Rathdown, County Dublin to Rathdown, County Wicklow after the Local Government (Ireland) Act 1898.[1][8]
^Clancy 1899, p.32 "It may be added that a rural district comprises the Union if such Union be situated wholly in one county, but if the Union extends into two or more counties the portion in each county becomes a rural district. In both cases urban sanitary districts are excluded.".