Rotary engine (disambiguation)
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

See also
 Radial engine, an internal combustion piston engines with a fixed engine block of radially-mounted cylinders driving a rotating crankshaft