Workers at Irish Rail have downed tools in a strike over pay today.
No Intercity, DART or commuter service trains are running in the city this morning and more than 150,000 passengers will be affected.
Train drivers are looking for a 3.75% pay rise in each of the next three years but Irish Rail say that's unaffordable.
"Rail tickets won't be valid on other operators services", says Barry Kenny from Irish Rail.
"We will be back fully tomorrow but we will refund customers for this disruption".
Commuters are being advised to leave extra time for their journeys. There are some extra private bus services running but demand is high.