The railway line closed by a freight train derailment in north Co Dublin last week reopened last night.
Iarnród Éireann crews worked over the weekend to repair the main northern line just south of Skerries.
Last night's final service between Belfast and Dublin Connolly was the first train travel on the line since the incident on Thursday night.
Iarnród Éireann said full services will operate on the Northern line commuter service and on the Dublin-Belfast service today, with possible slight delays and a 25mph speed restriction around the derailment site.
Investigations are continuing as to how six 75-tonne wagons carrying mineral ore left the tracks, blocking the line in both directions and causing major disruption for thousands of commuters after all peak hour services were cancelled on Friday morning.
Although a limited service was running by Friday evening when one of the lines were cleared, both tracks were closed again on Saturday and yesterday as engineers lifted the wagons and repaired the damaged track and sleepers.