David McGuinness has been selected by Fianna Fáil as its candidate to contest the by-election in Dublin West.
The by-election follows the death of former Minister for Finance Brian Lenihan.
Cllr McGuinness sits on Fingal County Council. He was elected in 2009 to represent the Mulhuddart area.
The 26-year-old ran in the General Election as Mr Lenihan's running mate, he won 623 first preference votes and was eliminated after the second count.
He is Fianna Fáil's youngest councillor.
A graduate of Trinity College Dublin, he teaches at Lucan Community College.