Windsor Railway Bridge is a wrought iron 'bow and string' bridge in Windsor, Berkshire, designed by Isambard Kingdom Brunel.
The bridge carries the ex-GWR branch line from Slough to Windsor into Windsor and Eton Central station. It crosses the River Thames on the reach between Romney Lock and Boveney Lock.
The bridge is a single-span structure comprising three bowstring trusses which created two bays for the original two GWR tracks. The bridge is the World's oldest wrought iron bridge still in regular service.
The line opened in 1849. The construction of the line was delayed and could not be included in the original Parliamentary Act because of objections from the Provost of Eton College.
The brick viaduct was constructed between 1861-65 to replace the original wooden trestle viaduct. The bridge contractor was George Hennet.
Although the bridge was built to take two tracks, the track on the upstream side was removed when the line was rationalised in the 1960s.
A drawing of the bridge as originally built shows that each of the three bowstring girders was supported at each end by a pair of 6 ft diameter cast iron cylinders. The clear span between the columns was 187 ft. The span was subsequently reduced by the iron columns being augmented by brickwork.