A double-decker bus is a bus which has two levels, typically seating 60-80 passengers. They were created as a means of carrying large numbers of passengers without exceeding legal limits on vehicle length, and are a common sight in many large cities in the United Kingdom. Double-decker buses are also used elsewhere in the world, but are not as common.

A particularly iconic example is the Routemaster bus which has been a staple of the public transport network in London for nearly half a century following its introduction in 1956. The last remaining examples in use are finally expected to be retired in 2005.