William Thorold (9 October 1798 – 17 December 1878)was an eminent 19th-century millwright, architect and civil engineer in Norwich, Norfolk, England. He was born in 1798 in Methwold, Norfolk, the son of a farmer. Apprenticed to George Shafto and later to John Fisher Gurling in St Martin's Lane, Norwich, he was in business as a millwright from 1828 until his death at his home in Thorpe Hamlet, Norwich, in 1878.