Ouse Valley Viaduct

The Ouse Valley Viaduct (or the Balcombe Viaduct) carries the Brighton Main Line over the River Ouse in Sussex, England. It is located to the north of Haywards Heath and the south of Balcombe. Known for its ornate design, the structure has been described as "probably the most elegant viaduct in Britain." Construction of the Ouse Valley Viaduct commenced by the London and Brighton Railway company the beginning of 1839.

It was designed by the principal engineer for the line, John Urpeth Rastrick. The architect of the London to Brighton railway, David Mocatta is often associated with the ornate stonework but an 1843 contemporary report on the construction of the viaduct makes no mention of him and neither does a drawing of one of the pavilions in a collection of Rastrick's drawings.

The viaduct is 96 feet (29 m) tall and is carried on 37 semi-circular arches, each of 30 feet (9.1 m), surmounted by balustrades, spanning a total length of 1,480 feet (450 m). Each pier contains a jack arch with a semi-circular soffit, which had the benefit of reducing the number of bricks required.

On 12 July 1841, the viaduct was officially opened to train services, although the finishing details were not fully completed until the following year. Despite the structure's fine design, materials, and architectural features, the viaduct has had an expensive and problematic history.