Thomas Horatio Nelson, 4th Earl Nelson (21 December 1857 – 30 September 1947), styled Viscount Merton until 1913, was a British peer, inheriting the earldom on 25 February 1913 from his father, Horatio Nelson, 3rd Earl Nelson. Born at Trafalgar Park in Wiltshire, he was the son of Horatio Nelson, 3rd Earl Nelson of Trafalgar and of Merton and Lady Mary Jane Diana (née Agar, 1823–1904). Thomas Nelson died in September 1947 at age 89. He never married and on his death the title passed to his younger brother Edward, the 5th Earl Nelson.