An electric bus is a bus that is propelled using electric motors, as opposed to a conventional internal combustion engine. Electric buses can store the needed electrical energy on board, or be fed mains electricity continuously from an external source such as overhead lines. The majority of buses using on-board energy storage are battery electric buses, where the electric motor obtains energy from an onboard battery pack, although examples of other storage modes do exist, such as the gyrobus that uses flywheel energy storage. When electricity is not stored on board, it is supplied by contact with outside power supplies, for example, via a current collector, or with a ground-level power supply, or through inductive charging.

A bus is a road vehicle that carries significantly more passengers than an average car or van, but less than the average rail transport. It is most commonly used in public transport, but is also in use for charter purposes, or through private ownership. Although the average bus carries between 30 and 100 passengers, some buses have a capacity of up to 300 passengers. The most common type is the single-deck rigid bus, with double-decker and articulated buses carrying larger loads, and midibuses and minibuses carrying smaller loads. Coaches are used for longer-distance services. Many types of buses, such as city transit buses and inter-city coaches, charge a fare. Other types, such as elementary or secondary school buses or shuttle buses within a post-secondary education campus, are free. In many jurisdictions, bus drivers require a special large vehicle licence above and beyond a regular driving licence.