William Benjamin Rounsevell (23 September 1843 – 18 July 1923), known as "Ben" or "Big Ben", was a South Australian politician. He was a member of the South Australian House of Assembly from 1875 to 1893 and from 1899 to 1906, representing the Burra and Burra Burra seats for all but one term, when he held Port Adelaide. He was Treasurer of South Australia four times: from May to June 1881 under William Morgan, from 1884 to 1885 under John Colton, from January to June 1892 under Thomas Playford II and from 1892 to 1893 under John Downer. He also served as Commissioner of Public Works from 1890 to 1892 under Playford, and again in the seven-day Solomon Ministry of 1899.[1] His brother, John Rounsevell, was also a South Australian politician.