Lansdowne Bridge, Historical sandstone bridge in New South Wales, Australia

Lansdowne Bridge is a single-arch sandstone bridge over Prospect Creek between Lansvale and Lansdowne in southwestern Sydney. Its clear span is 110 feet (34 m), with 76 feet (23 m) of clearance above mean water level at the centre. Curved abutments and approaches lead to simple parapets, and some radiating voussoirs measure up to eight feet (2.4 m) long.

The bridge was built from 1834 under the direction of David Lennox, using convict labor, and opened on January 26, 1836, the 48th anniversary of European settlement in the colony. Lennox was a Scottish stonemason who became the leading bridge builder in the colony.

The bridge takes its name from Henry Petty-Fitzmaurice, the 3rd Marquess of Lansdowne, a British statesman involved in colonial affairs during the 19th century. Crossing it today means following the same route that once connected Sydney to the interior of the continent.

The bridge sits along the Hume Highway southwest of Sydney and is easy to reach by car. Pedestrians can cross on foot, but should stay alert since vehicles pass regularly on the roadway.

The bridge's arch has a clear span of 110 feet (34 m), the largest of any surviving masonry bridge in Australia, with 76 feet (23 m) of clearance above mean water level at the centre. Its Hawkesbury sandstone was quarried at present-day East Hills, 11 km away, and rowed to the site by punt.