A rotary engine is a type of internal combustion piston engine used in some early aircraft, motorcycles, and cars. Almost the entire engine rotates about a fixed crankshaft.
Rotary engine may also refer to:
- Pistonless rotary engine, a type of pistonless internal combustion engine
- Turbine, a rotary engine that extracts energy from a fluid flow
- Wankel engine, a common type of pistonless rotary engine used in some NSU Motorenwerke AG (NSU) and Mazda cars
- Windmill, a rotary engine that extracts energy from wind
- Waterwheel, a rotary engine that extracts energy from water