John Callinan will become the new Secretary General at the Department of the Taoiseach, the Cabinet has agreed.
Mr Callinan had a leading role in co-ordinating the Government's response to Brexit.
He was the Second Secretary General at the Department of the Taoiseach since 2016 and was the Taoiseach's "sherpa" playing a key part in the Brexit negotiations.
He will replace the outing Secretary General Martin Fraser who has been appointed Ireland's ambassador in London.
That appointment was sanctioned last year but Mr Fraser remained in his role as the country's most high ranking civil servant until the Covid-19 crisis abated.
