A unit train is a railroad train in which all the cars typically travel from the same point of origin to the same destination, without being split up or stored en route. Unit trains are usually around 100-110 carriages long. Unit trains save time and money because they are not assembled and disassembled at rail yards near the origin or destination. It also enables railways to compete more effectively with road and internal waterway transport systems in keeping transportation costs for commodities low. However, unit trains are economical only for high-volume customers. Since unit trains often carry only one commodity, cars are typically of all the same type, and sometimes the cars are all identical apart from possible variations in livery.

Fuel ethanol? and feedstocks are often transported to and from biofuels production facilities by unit train.