The Belfast to Bangor line is a railway line in Northern Ireland, originally part of the Belfast & County Down Railway. All services are operated by NI Railways, the only operator for Northern Ireland (NI). Unlike the rest of the United Kingdom, no railway in NI is part of the National Rail network and none is owned by Network Rail. Services run every half-hour, with up to six trains per hour in each direction at peak times.

NI Railways, also known as Northern Ireland Railways, is the railway operator in Northern Ireland. NIR is a subsidiary of Translink, whose parent company is the Northern Ireland Transport Holding Company (NITHCo), and is one of eight publicly owned train operators in the United Kingdom, the others being Direct Rail Services, Northern Trains, Transport for Wales Rail, Southeastern, LNER, ScotRail, and TransPennine Express. It has a common Board of Management with the other two companies in the group, Ulsterbus and Metro.