An overhead line, or overhead wire, is used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point. It is known variously as

In this article the generic term overhead line is used. This is also the term used by the International Union of Railways.

Overhead line is designed on the principle of one or more overhead wires or rails (particularly in tunnels) situated over rail tracks, raised to a high electrical potential by connection to feeder stations at regular intervals. The feeder stations are usually fed from a high-voltage electrical grid.