Gasoline (or petrol) engine or Otto engine from Nikolaus Otto is a type of internal combustion engine which is often used for automobiles, aircraft, small mobile vehicles such as lawnmowers or motorcycles, and outboard motors for boats.

The most common engine of this type is a four stroke cycle internal combustion engine that burns gasoline (in American English) or petrol (British English). Burning is initiated by an ignition system that fires a high voltage spark through a sparkplug. The two stroke cycle type of engine is often used for smaller, lighter and cheaper applications but it is less fuel efficient.

Wankel engines can also use gasoline as their fuel.

One component in older engines is the carburator, which mixes the gasoline with air. In later engines the carburetor is replaced with fuel injection.