William Fitzwilliam, 4th Earl of Southampton (1783-1854), was a British nobleman and politician. He inherited the title from his father, the 3rd 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 Hastings and Southampton. The 4th Earl was also a patron of the arts and contributed to various charitable causes. He was associated with the Whig Party, which advocated for political reform and social progress during his time. His legacy includes his efforts in promoting education and public welfare in his community.