President Mary McAleese has formally appointed Mr Justice John Murray as Chief Justice at a signing ceremony in Áras an Uachtaráin.
In accordance with constitutional procedures, the Taoiseach, the Minster for Justice and the Attorney General also attended the ceremony where Mr Justice Murray was presented with a warrant formalising his appointment.
Mr Justice Murray's nomination was widely welcomed by legal experts and political leaders earlier this week. He is regarded as one of the most experienced members of the judiciary and is the only former attorney general now sitting on the bench.
He has served 10 years at the European Court of Justice and five years on the Supreme Court.