The Mercedes-Benz M120 engine is a naturally aspirated high-performance automobile piston V12 engine family used in the 1990s and 2000s in Mercedes' flagship models. The engine was a response to BMW's M70 V12 engine, introduced in 1987. While the 5-litre BMW unit developed 300 metric horsepower (220 kW), Mercedes-Benz upped the ante considerably by creating a 6-litre, 300-kilowatt (408 PS) engine.

A V12 engine is a twelve-cylinder piston engine where two banks of six cylinders are arranged in a V configuration around a common crankshaft. V12 engines are more common than V10 engines. However, they are less common than V8 engines.