William Joseph Denison (May 1770 - 2 August 1849) was an English banker and politician.
William was successful in, and became senior partner of, Denison, Heywood, & Kennard, bankers, in Lombard Street. He sat in Parliament as a Whig for Camelford 1796-1802, was elected for Kingston upon Hull in 1806, and was the member for Surrey from 1818 until 1832, and then West Surrey until his death.
He inherited estates in Surrey (Denbies) and Yorkshire (Seamer) on the death of his father in 1806. During his lifetime Denison increased his father's large fortune and added to the Denbies estate.
His death took place in Pall Mall, London on 2 August 1849. Worth an estimated £2,300,000, he died unmarried, and left virtually all of his wealth to his nephew Lord Albert Conyngham, on condition that he took the name Denison. According to the records of The General Cemetery Company (incorporated by Act of Parliament 1832), Denison is buried in plot 8304 in Kensal Green Cemetery.