An incendiary balloon is a balloon inflated with a lighter-than-air gas such as hot air, hydrogen, or helium, that has a bomb, incendiary device, or Molotov cocktail attached. The balloon is carried by the prevailing winds to the target area, where it falls or releases its payload.

Operation Outward was a British campaign of the Second World War that attacked Germany and German-occupied Europe with free-flying balloons. It made use of cheap, simple balloons filled with hydrogen and carrying either a trailing steel wire to damage high voltage power lines by producing a short circuit, or incendiary devices to start fires in fields, forests and heathland. A total of 99,142 Outward balloons were launched; about half carried incendiaries and half carried trailing wires.