AIB and Bank of Ireland are looking to sell off around 1,000 ATMs between them.
The cash machines up for sale represent more than a quarter of all ATMs in the country.
Bank of Ireland is selling off a network of 700, while AIB is seeking bids for 375.
However, there are concerns that fees at machines will increase as a result.
Consumer groups say companies that own ATMs independently of banks are likely to impose charges and fees for using them.
Speaking on Newstalk's The Pat Kenny Show, Charlie Weston, a journalist from the Irish Independent, says that new charges would be on top of fees already imposed by banks.
He said: "If you go to an independently operated ATM, the risk is that they will decide over time to introduce charges, so you could be talking about €1 every time you withdraw cash or it could even be €3.
"If an Irish person goes to New York and you go to an independently operated ATM, it's not uncommon to be charged $3 per withdrawal."
He added that the traditional ways of banking are slowly fading away.
Mr Weston said: "People are very much moving away from cash and you can now use your phone.
"People are less inclined to use cash.
"The danger there is that you don't feel you're spending as much, it's too easy to spend and you cant keep as good a mental record when you're tapping.
"But inevitably that's the way we're moving I'm afraid."
The machines being sold by both AIB and Bank of Ireland are largely based in retail outlets.
There are currently around 3,000 ATMs owned by banks nationwide, and another 750 owned by independent providers.
Reporting by Seán O'Regan