Services vary depending on region.
Today, Christmas Eve, Bus Éireann city, town, commuter and rural services will operate a weekday service with last departures at 21:00.
It says the Expressway interregional services will operate as normal with last departures varying for each service.
Bus Éireann has advised customers to visit the expressway website for more information, where guaranteed seats can be booked online.
There will be no Bus Éireann services on Christmas Day.
Services resume on St. Stephen's Day, where Bus Éireann city, town, commuter and rural services will operate a Sunday/Bank Holiday service with first departures from 9:00.
Expressway services will also operate a Sunday/Bank Holiday service with first departures varying for each service.
Services from Monday 27 December to Friday 31 December inclusive will operate to a weekday schedule.
For details on what services will be operating over the Christmas holidays, visit the Bus Éireann website.
Bus Éireann says services are operating at 100% capacity.
Bus Éireann is advising customers to continue to wear face coverings within bus stations and on board throughout their entire journey.