AIB is to close 15 of its branches and merge them with other nearby locations.
The bank says this is due to increased customer digital usage and declining branch visits.
It says customers are interacting with its app more than 1.54 million times a day - compared with 35,000 daily branch visits.
The move follows a detailed strategic review, which it says has been accelerated by the pandemic.
In a statement, the bank says: "These changes, and some service overlaps, mean the bank is merging a number of branches.
"The amalgamation of these branches will happen on a phased basis, commencing in September 2021 and to be completed by December 2021.
"As with previous branch re-organisations, there will be no compulsory redundancies."
The vast majority of the branch amalgamations are in urban/suburban locations, mostly Dublin and Cork.
A full list of branch closures is available here
The bank says it will communicate details to its customers, who do not need to take any action.
As part of the changes AIB is to extend a partnership with An Post, providing customers with access to cash services in over 900 post offices offices.
AIB managing director of retail banking, Jim O'Keeffe, says: "We remain committed to maintaining a strong presence in the communities we serve throughout Ireland, and we will continue to do so with over 170 branches.
"However, inevitably and in line with the evolution of banking and customer needs, we are seeing a requirement to evolve our services to customers.
"We will do everything we can to guide our customers through the transition as we take another step towards ensuring a sustainable future for AIB's branch network."
This is the latest change to the Irish banking landscape, after Bank of Ireland announced plans to close 88 branches earlier this year.
Again, Bank of Ireland put the changes down to a bigger uptake in digital banking.
And it also has a partnership with An Post to offer customers the ability to access services.