Ulster Bank says it will close “in the region” of 20 branches and sub-offices in Ireland this year.
The bank said it will provide further details on the closures to customers and employees within the next few weeks.
The bank has 146 branches in the Republic of Ireland and 90 in Northern Ireland.
Royal Bank of Scotland, which owns Ulster Bank, has injected at least £10.8 billion into the bank since 2008 to absorb losses after the property market downturn.
Ulster Bank’s operating loss widened in the first nine months of last year to £797m from £751m the same time in 2011, as a fall in interest income offset stabilising loan losses.
RBS acquired Ulster Bank in 2000 as part of its purchase of National Westminster Bank and expanded three years later through the acquisition of the First Active building society.
Ulster Bank joins the ranks of a growing number of banks that have significantly reduced their branch network in recent years as part of significant cost cutting measures.