An Post has revealed the locations of 159 post offices set to close.
This is because the serving postmaster has opted to retire.
Earlier this month, the company offered a voluntary retirement package to 161 postmasters.
An Post says businesses will transfer to neighbouring offices at a number of locations.
In a statement, the firm says: "Post offices in locations where postmasters are opting to retire will close and the services will be consolidated with neighbouring offices ensuring their continued viability.
"Sixteen such post offices have already closed at the request of the retiring contractor."
The changes will affect post offices all over the country.
These include Carlow, Clare, Cork, Donegal, Galway, Kerry, Mayo, Tipperary and Wexford.
An Post says: "All remaining post offices will benefit from enhanced services and products, new opening hours and an investment package aimed at improving services for customers, driving customer footfall and attracting a wider demographic to ensure that the post office is not just wanted by communities but is indeed relevant and actually used by all."
Debbie Byrne is managing director of An Post Retail.
She thanked the postmasters who have chosen to retire for their "great service to An Post and local communities".
She also says An Post is "committed to ensuring the sustainability and viability of the post office network and would move now to offer more new and innovative services to customers through the reconfigured network."