Allied Irish Banks was formed in 1966, bringing together three distinctive Irish banking traditions. The Provincial Bank, founded in 1825, pioneered branch banking in Ireland. The Royal Bank, established eleven years later, was famous for its mercantile links. The Munster & Leinster, formed in 1885, was the largest of the three banks with the most extensive branch network.

AIB Group is Ireland's leading banking and financial services organisation. It operates principally in Ireland, Britain, Poland and the USA. It employs more than 22,000 people worldwide in more than 750 offices.

More than three decades since its formation, AIB is a dynamic and successful organisation. In 1966, AIB's aggregate assets were €323.8 million – as at 31 December 2004, the AIB Group had assets of €102 billion.