Knorr-Bremse AG is a German manufacturer of braking systems for rail and commercial vehicles that has operated since 1905. Other products in Group's portfolio include intelligent door systems, control components, air conditioning systems for rail vehicles, torsional vibration dampers, and transmission control systems for commercial vehicles. In 2022, the Group's workforce of over 31,000 achieved worldwide sales of EUR 7.15 billion.

An air brake or, more formally, a compressed-air-brake system, is a type of friction brake for vehicles in which compressed air pressing on a piston is used to both release the parking/emergency brakes in order to move the vehicle, and also to apply pressure to the brake pads or brake shoes to slow and stop the vehicle. Air brakes are used in large heavy vehicles, particularly those having multiple trailers which must be linked into the brake system, such as trucks, buses, trailers, and semi-trailers, in addition to their use in railroad trains. George Westinghouse first developed air brakes for use in railway service. He patented a safer air brake on March 5, 1872. Westinghouse made numerous alterations to improve his air pressured brake invention, which led to various forms of the automatic brake. In the early 20th century, after its advantages were proven in railway use, it was adopted by manufacturers of trucks and heavy road vehicles.