An election to the urban district council of Rathmines and Rathgar took place on Thursday, 15 January 1920 as part of the 1920 Irish local elections.
The Local Government (Ireland) Act 1919 had changed the electoral system for local government in Ireland from first-past-the-post to single transferable vote.
The election saw Unionists reduced to a majority of 1 on the council.
Prior to the election the Rathmines and Rathgar council had been composed almost entirely of Unionists.
Ceannt lost to Ireland by a single vote.