Bank of Ireland says it's closing 88 of its branches here due to a rise in digital banking.
15 more are to close in the North with the closures coming into effect by September.
Around 200 staff work in these branches but management say there will be no compulsory redundancies.
Ballyhaunis, Charlestown and Kiltimagh are the branches of the bank set to close in Mayo.
While in county Galway the branches to close are Ballygar, Dunmore and Oughterard.
In Roscommon, Elphin and Strokestown branches are to close.
While the BOI branches in Ballymote and Tubbercurry are to close in Sligo.
The branches, due to close by the end of September, are described by the bank as "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.
However, the decision to close around a third of Bank of Ireland branches has been described as a bolt out of the blue.
John O'Connell from the Financial Services Union says the branches mean a lot to local communities.