William Fitzwilliam, 6th Earl of Southampton (1783-1854) was a British nobleman and politician. He inherited the title from his father, the 5th Earl, and was known for his involvement in local governance and the House of Lords. He served as a Member of Parliament for several constituencies, including Southampton. The 6th Earl was also a patron of the arts and contributed to various charitable causes. He was associated with the Whig Party, which supported reform and liberal policies during his time. His legacy includes his efforts in promoting social improvements and his influence in the political landscape of 19th-century Britain.