A train driver, engine driver, engineman or locomotive driver, commonly known as an engineer or railroad engineer in the United States and Canada, and also as a locomotive handler, locomotive engineer, locomotive operator, train operator, or motorman, is a person who operates a train, railcar, or other rail transport vehicle. The driver is in charge of and is responsible for the mechanical operation of the train, train speed, and all of the train handling (also known as brake handling). In American English, a hostler (also known as a switcher) moves engines around rail yards, but does not take them out on the main line tracks; the British English equivalent is a shunter.

Train drivers must follow certain guidelines for driving a train safely. For instance, in general, train drivers are encouraged to favour longer stopping distances as this promotes vehicle health, safety, and passenger comfort.