Bus Éireann is to cease operating three of its Expressway services from Sunday, 24 May.
The services that are to be withdrawn include Waterford - Dublin/Dublin Airport (Route 4), Rosslare/Wexford - Waterford (Route 40 Segment), and Ballina - Galway (Route 52).
The bus operator has said the "significant" financial losses that these services are incurring was the reason for it taking the decision.
The National Transport Authority has been notified about the matter.
With 12 services daily, Bus Éireann previously described its Route 4 service as the "key" to the south east of the country.
The route between Dublin and Waterford also services parts of Carlow and Kilkenny.
A spokesperson for Bus Éireann said Expressway is a "commercial service, which receives no State subvention."
"The measures announced are in response to the continuous significant losses being incurred on these services.
"While disappointing, it is clearly unsustainable for a commercial operation.
"The decision to consolidate our Expressway network and withdraw from a small number of routes is aimed at safeguarding the Expressway network.
"Given the scale of our operations, there will be no impact on jobs given our current recruitment needs.
"Any customer who has a pre-booked journey on any of the impacted services will be contacted and provided with a full refund," the spokesperson added.
The Route 40 service currently runs between Rosslare Europort in Co Wexford and Tralee, Co Kerry.
The service will cease servicing Rosslare Europort, Wexford town, New Ross and Ferrybank under the planned changes that are due to take affect from 24 May.
The Route 40 service will continue operating between Waterford and Tralee.
With six services departing from Ballina and Galway every day, the Expressway Route 52 that is due to cease also passes through Foxford, Castlebar, Claremorris and Tuam.
