|Birth date||November 28, 1810|
|Date of death||May 4, 1879|
|Place of death||Simonstown, South Africa|
William Froude (pronounced /ˈfruːd/) (November 28, 1810 in Devon  – May 4, 1879 in Simonstown, South Africa) was an English engineer, hydrodynamicist and naval architect. He was the first to formulate reliable laws for the resistance that water offers to ships (such as the hull speed equation) and for predicting their stability.
His first employment was as a surveyor on the South Eastern Railway which, in 1837, led to Brunel giving him responsibility for the construction of a section of the Bristol and Exeter Railway. It was here that he developed his empirical method of setting out track transition curves and the geometry of masonry skew bridges.
At Brunel's invitation Froude turned his attention to the stability of ships in a seaway and his 1861 paper to the Institution of Naval Architects became influential in ship design. This led to a commission to identify the most efficient hull shape, which he was able to fulfil by reference to scale models: he established a formula (now known as the Froude number) by which the results of small-scale tests could be used to predict the behaviour of full-sized hulls. His experiments were vindicated in full-scale trials conducted by the Admiralty and as a result the first ship test tank was built, at public expense, at his home in Torquay. Here he was able to combine mathematical expertise with practical experimentation to such good effect that his methods are still followed today.
He died while on holiday (as an official guest of the Royal Navy) in Simonstown, South Africa and was buried there with full naval honours. He was the brother of James Anthony Froude, a historian, and Hurrell Froude, writer and priest. William was married to the former Catherine Henrietta Elizabeth Holdsworth, daughter of Dartmouth Governor, mercantile magnate and member of Parliament Arthur Howe Holdsworth.