Birkenhead Bridge, Bascule bridge in Port Adelaide, Australia.

Birkenhead Bridge is a bascule bridge crossing the Port River with a double-leaf mechanism that raises to let ships pass underneath. The structure stretches across the waterway and links the suburbs of Birkenhead and Port Adelaide by road.

In February 1938 the South Australian government awarded Adelaide Construction the contract to build a bridge from Birkenhead to Port Adelaide, with Perry Engineering supplying the steelwork. Governor Malcolm Barclay-Harvey opened it on 14 December 1940. It was one of only four bascule bridges in the world adapted for trolleybus use, and it is listed on the South Australian Heritage Register.

The bridge's name comes from the Birkenhead suburb on its western bank, and it is listed on the South Australian Heritage Register. Its bascule leaves still lift for river traffic, and since 2014 two of the four road lanes have served pedestrians and cyclists crossing between Birkenhead and Port Adelaide.

The bridge carries regular traffic between the two suburbs and has separate paths for pedestrians and cyclists to use safely. The roadway lifts periodically to allow water traffic to pass, so check for any raised-bridge notices before planning your crossing.

The structure was originally designed with dedicated lanes for trolleybuses, making it one of only a handful of bascule bridges worldwide built for this specific transit mode. This unusual feature shows how engineers planned for diverse transportation needs in that era.