AIB's deputy chairman, Dr Michael Somers, will stand down from the company at the end of this month.
Dr Somers, who is also an independent non-executive director, will resign in line with the terms of his appointment, the bank said.
A former chief executive of the National Treasury Management Agency (NTMA), Dr Somers was appointed to AIB by the government after the global financial crash.

Catherine Woods will replace Dr Somers as deputy chairman of the bank from January 1st next year, while continuing in her roles as senior independent non-executive director and chairman of the board audit committee. Ms Woods is a former head of European banks equity research at JP Morgan and is currently a non-executive director of global insurance business, Beazley.
"I thank Michael Somers for his service on the Board. His retirement creates a vacancy for Deputy Chairman which will be filled by Catherine Woods. Catherine has been an excellent Senior Independent Director and chair of the Audit Committee and I look forward to working with her in this additional role," Richard Pym, the bank's chairman, said.