Brian Carr has been co-opted onto Donegal County Council.
He replaces Councillor Marie Therese Gallagher who is on maternity leave of absence.
Mr Carr was selected by Sinn Fein to contest the local elections in June in the Glenties Local Electoral Area.
Tributes have been paid to Councillor Gallagher today.
She has confirmed that she will not be seeking re-election in the upcoming elections.
