An alley or alleyway is a narrow lane found in urban areas, often for pedestrians only, which usually runs between or behind buildings. In older cities and towns in Europe, alleys are often what is left of a medieval street network, or a right of way or ancient footpath in an urban setting. In older urban development, alleys were built to allow for deliveries such as coal to the rear of houses. Alleys may be paved, or simply dirt tracks. A blind alley has no outlet at one end and is thus a cul-de-sac.

Many modern urban developments do not incorporate alleys, but some may provide a service road to allow for waste collection, or rear access for fire engines and parking. Andrés Duany, American architect and urban planner, has long espoused the use of alleys as leading to a better integration of automobile and foot traffic in a neighborhood.^{[citation needed]}