Thomas Fitzwilliam, 6th Earl of Southampton (1701–1786), was a British nobleman known for his role in the English peerage. He inherited the title from his father, Thomas Fitzwilliam, 5th Earl of Southampton, and was involved in various political and social activities during his lifetime. He was a member of the House of Lords and participated in the governance of England. The 6th Earl was also known for his contributions to the arts and culture, supporting various initiatives that promoted literature and the fine arts during the 18th century.