Sir William Cubitt FRS (bapt. 9 October 1785 – 13 October 1861) was an eminent English civil engineer and millwright. Born in Norfolk, England, he was employed in many of the great engineering undertakings of his time. He invented a type of windmill sail and the prison treadwheel, and was employed as chief engineer, at Ransomes of Ipswich, before moving to London. He worked on canals, docks, and railways, including the South Eastern Railway and the Great Northern Railway. He was the chief engineer of Crystal Palace erected at Hyde Park in 1851.