North Down Alliance Association has selected Andrew Muir to replace David Alderdice as a member of North Down Borough Council, representing the Holywood area.
Mr Alderdice recently announced his resignation from the council due to work pressures.
Mr Muir, 33, was born and raised in North Down, holds a degree in Peace and Conflict Studies from the University of Ulster and works as a manager with Translink.
He said: “I am extremely grateful for the excellent legacy left by David and am looking forward to serving the people of Holywood, building a shared future and safeguarding the environment as part of a strong Alliance team on North Down Borough Council.”
Under electoral law, the council chief executive will notify the chief electoral officer about the vacancy.
He in turn will write to the leader of the Alliance Party, David Ford, seeking a nomination to fill that vacancy. Under Alliance procedures, the party leader will follow the decision of the local association.