Fianna Fáil has selected Councillor David McGuinness as its candidate to contest the forthcoming by-election in Dublin West.
The by-election will take place on the same day as the Presidential election - October 27 - and follows the death earlier this year of former Finance Minister, Brian Lenihan.
Councillor McGuinness, who is 25 and the party's youngest councillor, teaches at Riversdale community college in Corduff.
He was first elected in 2009 to represent the Mulhuddart area on Fingal Council.
He ran in the General Election and won 623 first preference votes and was eliminated after the second count.