Bank of Ireland is closing 88 branches in the Republic, and 15 in Northern Ireland.
The branches, due to close by the end of September, are mainly self-service which don't have a counter service.
It says they all have a post office within 500 metres on average.
The bank is entering into a new partnership with An Post to offer banking services at over 900 locations, with longer opening hours.
Francesca McDonagh, Group CEO of Bank of Ireland, says details of the branch closures will be announced later: