An overhead line or overhead wire is used to transmit electrical energy to trams, trolleybusses, or trains. It is known variously as:

In this article, the generic term overhead line is used, as 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.