This constituency comprised the southern part of
County Mayo. In 1918, the constituency expanded to take in the
district electoral divisions of Ballinchalla and Owenbrin from
County Galway which had been transferred into County Mayo under the 1898 Local Government Act.
1885–1918: The baronies of
Clanmorris and
Kilmaine, that part of the barony of Costello contained within the parishes of Aghamore, Annagh, Bekan and Knock, and that part of the barony of Carra contained within the parish of Ballyovey.
1918–1922: The existing South Mayo constituency together with that part of the
Galway Connemara constituency contained in the administrative county of Mayo. ==Members of Parliament==