The Tamar Bridge is a suspension bridge over the River Tamar between Saltash, Cornwall and Plymouth, Devon in southwest England. It is 335 metres (1,099 ft) long, running adjacent the Royal Albert Bridge, and part of the A38, a main road between the two counties.

During the 20th century, there was increasing demand to replace or supplement the Saltash and Torpoint ferries, which could not cope with the rise in motor traffic. The Government refused to prioritise the project, so it was financed by Plymouth City Council and Cornwall County Council. Construction was undertaken by the Cleveland Bridge & Engineering Company and began in 1959. It was unofficially opened in October 1961, with a formal presentation by Queen Elizabeth The Queen Mother in April 1962. A reconstruction of the bridge began in 1999 after it was found to be unable to support a European Union requirement for goods vehicle weights. The work involved building two new parallel decks while the original construction was completely rebuilt. The project was completed in late 2001 and formally opened by Princess Anne in April 2002. The extra decks have remained in use, increasing the bridge's capacity.

The bridge is tolled for eastbound travel, with a discount available via an electronic payment scheme. It has become a significant landmark in Plymouth, Saltash and the surrounding area, and used on several occasions for protests or to highlight the work of charities and fundraisers.

The bridge runs over the River Tamar from near Wearde, Saltash in the west to Riverside, Plymouth in the east. It has a central span of 335 metres (1,099 ft) and two side spans of 114 metres (374 ft). It is part of the A38, a major cross-country road that runs across Cornwall and Devon, and lies immediately north of the Royal Albert Bridge, a significant railway bridge designed by Isambard Kingdom Brunel that opened in 1859. Both bridges are north of the Hamoaze, the estuary that the Tamar feeds into, and the Torpoint Ferry.

In 1961, approximately 4000 vehicles used the Tamar Bridge each day. This significantly increased in the following decades; in 1998 the hourly rate during the morning rush hour was 2500 vehicles. The average weekday saw 38,200 vehicles cross the bridge and the summer weekday flow was 42,900. Conversely, the Torpoint ferry link could transport a maximum of 300 vehicles per hour.

The bridge is owned and maintained by the Tamar Bridge and Torpoint Ferry Joint Committee, a conglomerate between Plymouth City Council and Cornwall County Council. It has a main span of three lanes, which use a tidal flow arrangement to maximise traffic flow at rush hour, and two outer lanes. The north of these is used as a local access route from Saltash, while the south is used by cyclists and pedestrians but could be converted to meet future vehicle demand if alternatives for pedestrians and bicycles were provided, a dedicated ferry, shuttle bus, cable car or bridge have been considered. The bridge capacity is around 1,800 vehicles per hour per lane over each main and added decks:

The toll booth capacity in the eastbound direction only as operated in 2013 was 4,200 vehicles per hour and not considered to be constraining the route flow even though it's less than the potential eastbound 5,400 vehicles per hour from two main lanes and Saltash local.^{[citation needed]}

The initial toll for cars was 3s (15p) for a single journey across the bridge, or 4/6 (22½p) for a return, while for lorries it was 14s (70p) and £1 respectively. The Saltash Ferry closed, but the Torpoint Ferry remained in operation; management of the ferry and the bridge is shared so the two crossings are not in direct competition with each other.