The former AIB executive had been chairman of the supervisory board of Santander Bank Polska – which emerged from AIB’s former Polish division Bank Zachodni, which Byrne joind in 2001.
AIB was forced to sell the Polish business in 2010 as a condition of its bailout.
Banco Santander is the largest bank in the euro zone by market capitalisation.
Gerry Byrne’s appointment is part of a wider reorganisation at the Spanish banking giant.
He is a graduate of Harvard Business School, the Irish Management Institute and Institute of Bankers in Ireland.
Before moving to Poland he was managing director of AIB’s then ARK Life Assurance business.