The Great Northern Railway of Ireland (GNRI) AEC Class were Associated Equipment Company (AEC)–engined diesel multiple units (normally termed railcars in Ireland) that operated InterCity and suburban services on the GNRI and later Ulster Transport Authority (UTA) systems between 1950 and 1975.

After 1945 the GNR(I) found itself in a poor financial position as a result of the deprivations of World War II and increased competition from road traffic.

Along with diesel locomotives, railcars offered a cheaper and more flexible means of traction than steam-hauled coaches.

These cars, based on a 1930s AEC/Great Western Railway design, were powered by two AEC underfloor engines of 125 hp (93 kW), each one driving the inner axle of one bogie through a five-speed, pre-selective epicyclic gearbox.

The design incorporated a full width cab at the front and a guard's and luggage compartment at the rear, as well as a steam-generating unit.

Some of CIÉ AECs were converted to push-pull driving car in 1973–74 for use on Dublin suburban services, propelled by rebuilt CIE 201 Class diesel locomotives.

An 00 gauge model of a Park Royal AEC railcar is available as an etched-brass kit from Worsley Works.