Passengers are being advised that reduced timetables are in place as tens of thousands of people are expected to use public transportation on the last day before Christmas.
Iarnród Éireann is advising Christmas Eve passengers to prebook their tickets before making their journey.
It said DART and commuter trains are operating on a "normal Saturday service" and the last trains will be between 7.25pm and 9pm.
The last service from Dublin Heuston to Portlaoise will depart at 7.45pm and the last train leaving Portlaoise to Dublin will leave at 7.25pm.
The final train to Maynooth from Dublin Connelly is scheduled for 8.17pm and the last service from Maynooth to Dublin Connelly is at 9.08pm.
The last service to M3 Parkway will leave Clonsilla at 8.50pm and the final train will leave the Co Meath station at 9.08pm in the other direction.
The final Dublin Connelly service to Drogheda will depart at 8.18pm, while the final Drogheda to Dublin train is at 7.48pm.
The last DART from Malahide will leave at 9.03pm and in the other direction, the final service will depart Bray at 8.57pm.
Iarnód Éireann also said the Phoenix Park Tunnel Commuter (Grand Canal Dock/Hazelhatch and Newbridge) route will operate a reduced service.
The final Hazelhatch to Grand Canal Dock service will leave at 6.52pm and the final train in the opposite direction is at 7.45pm.
Commuter lines in Cork will also operate a Saturday service until around 8pm and 9pm.
The last service to Cobh will depart Cork at 8pm and 8.30pm from in the opposite direction.
The final train from Cork to Midleton leaves at 8.15pm and 8.45pm the other way.
Iarnród Éireann said there will be no train services tomorrow and St Stephen's Day.
Anyone travelling on the Luas is advised that services will end at 8pm, with no services tomorrow.
The Luas will resume operations at 9am on St Stephen’s Day.
Dublin Bus said a weekday service will be in operation on all routes with the last departures at around 9pm, including on routes that run 24 hours normally.
There will be no buses running in the capital tomorrow.
There will be a Sunday service in operation on St Stephen's Day and routes 15, 39a, 41, C1, C2, C5, C6, G1, G2 and N4 will operate from 5am.
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