An electro-diesel locomotive is a type of locomotive that can be powered either from an electricity supply or by using the onboard diesel engine. For the most part, these locomotives are built to serve regional, niche markets with a very specific purpose.

A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the use of these self-propelled vehicles is increasingly common for passenger trains, but rare for freight trains.