The FL-boat (Fernlenkboot, literally "remote controlled boat") was a weapon used by the Imperial German Navy during World War I.

It was a remote-controlled motorboat, 17 m long, carrying 700 kilograms (1,500 lb) of explosives, which was intended to be steered directly at its targets - initially the Royal Navy monitors operating off the coast of Flanders.

They were driven by internal combustion engines and controlled remotely from a shore station through spooled wire unwound behind the boat.

The wire was 20 kilometres (12 mi) long and the spool weighed 800 kilograms (1,800 lb).

The commands available to the boat operator were: Planned developments were to use a control station carried on a ship, in an airship or use a radio-control system.