The Wankel engine (ˈvaŋkəl̩, Vann-KELL) is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. It was invented by German engineer Felix Wankel, and designed by German engineer Hanns-Dieter Paschke. The Wankel engine's rotor, which creates the turning motion, is similar in shape to a Reuleaux triangle, with the sides having less curvature. The rotor rotates inside an oval-like epitrochoidal housing, around a central output shaft. The rotor spins in a hula-hoop fashion around the central output shaft, spinning the shaft via toothed gearing.

Due to its inherent poor thermodynamics, the Wankel engine has a significantly worse thermal efficiency and worse exhaust gas behaviour when compared against the Otto engine or the Diesel engine, which is why the Wankel engine has seen limited use since its introduction in the 1960s. However, its advantages of compact design, smoothness, lower weight, and fewer parts over the reciprocating piston internal combustion engines make the Wankel engine suited for applications such as chainsaws, auxiliary power units, loitering munitions, aircraft, jet skis, snowmobiles, and range extenders in cars. In the past, the Wankel engine has also been used in road vehicles such as motorcycles, and racing cars.