The Forth Rail Bridge, a cantilever bridge with three double cantilevers

A cantilever bridge is a bridge whose structure is supported using the technique of cantilevers. Unlike suspension bridges where the load is supported at either end of the bridge, the strength of a cantilever bridge comes from a structure or structures positioned towards the middle of the bridge.

The bridge usually consists of three spans, with the ground or footing supports at either end of the bridge providing additional anchorage for the two outer spans, and the central cantilevers, positioned over the channel that is being crossed, providing the support for a central span. This span may be lifted into place or may be constructed using special traveling supports which are themselves also cantilevers. Usually the bridge's cantilevers are in identical pairs, but this is not required, provided that they are either balanced or supported until attached to appropriately massive outer foundations. The cantilevers support loads by tension of the upper beams and compression of the lower ones. The structure then distributes such tension to the supports at the shore, and the compression is usually carried to the foundations beneath the central towers.

The term 'cantilever bridge' is also used in dentistry to refer to a dental bridge that is attached to adjacent teeth on one end only.

World's longest cantilever bridges (by longest span)

1. Quebec Bridge (Quebec, Canada) 550m
2. Forth Rail Bridge (Firth of Forth, Scotland) 2 x 521m
3. Commodore Barry Bridge (Pennsylvania, USA) 501m
4. Greater New Orleans Bridge (Louisiana, USA) 480m
5. Howrah Bridge (Calcutta, India) 457m