The Trans-Dublin is a railway route serving the city of Dublin and its surrounding areas. The route is used primarily by the DART service, and runs North-South along the east coast of Ireland. The route is divided into two parts over two different railway lines:

• Belfast to Dublin main line - This runs from Dublin Connolly to Belfast Central. The northern section of the Trans-Dublin operates between Dublin Connolly and Howth Junction, where it branches off. The main line continues to Malahide, while a short branch terminates at Howth.
• Dublin to Rosslare main line - This runs from Dublin Connolly to Rosslare Europort. The southern half of the Trans-Dublin runs as far as Greystones in County Wicklow.