British Rail produced a variety of railbuses, both as a means of acquiring new rolling stock cheaply, and to provide economical services on lightly used lines.

A railbus is a lightweight passenger railcar with an automotive engine. They shares many aspects of its construction with a bus, typically having a bus body and four wheels on a fixed base instead of on bogies. Originally designed and developed during the 1930s, railbuses have evolved into larger dimensions with characteristics similar in appearance to a light railcar, with the terms railcar and railbus often used interchangeably. Railbuses designed for use specifically on little-used railway lines were commonly employed in countries such as Germany, Italy, France, the United Kingdom, and Sweden.