A street lamp is a raised source of light on the edge of a road, which is turned on or lit at a certain time every night. Modern lamps may also have light-sensitive photocells to turn them on at dusk, off at dawn, or activate automatically in dark weather. In older lighting this function would have been performed with the aid of a solar dial. It is not uncommon for street lights to be on posts which have wires strung between them, such as on telephone poles or utility poles.

The elevated light illuminates the road environment during darkness. Its control can follow a schedule or respond to the available daylight.

The lamp may share a utility pole with other equipment rather than having a dedicated post. An aircraft warning light instead alerts pilots to an obstruction.