Charles William Wentworth Fitzwilliam, 3rd Earl Fitzwilliam in the peerage of Great Britain, and 5th Earl Fitzwilliam in the peerage of Ireland KG (4 May 1786 – 4 October 1857) was a British nobleman and politician. He was President three times of the Royal Statistical Society in 1838–1840, 1847–1849, and 1853–1855; and President of the British Association for the Advancement of Science in its inaugural year (1831–2).
He was born the only son of William Fitzwilliam, 4th Earl Fitzwilliam and his first wife, Lady Charlotte Ponsonby. He was a pupil at Eton College from 1796 to 1802.
Before inheriting the Earldom on 8 February 1833 on the death of his father, he was known by the courtesy title of Viscount Milton. Under that name he was the Whig Member of Parliament for Northamptonshire between 1831 and 1832.
He married the Hon. Mary Dundas (30 May 1787 – 1 November 1830) on 8 July 1806; she was his cousin and the daughter of Thomas Dundas, 1st Baron Dundas and Lady Charlotte Fitzwilliam, the 4th Earl's sister. They had 13 children: