Louis Frederick John Spencer, Viscount Althorp (born 14 March 1994), is a British aristocrat who is a member of the Spencer family. He was born in Westminster, London, the fourth child and eldest son of Charles Spencer, 9th Earl Spencer, and his first wife, Victoria Lockwood. Nephew of Diana, Princess of Wales, and first cousin of Prince William, Duke of Cambridge, and Prince Harry, Duke of Sussex, he is the heir apparent to the earldom of Spencer.
Lord Althorp was a pupil at Diocesan College in Cape Town, and is currently enrolled at the University of Edinburgh.
English primogeniture law dictates that Lord Althorp, not his eldest sister, Lady Kitty Spencer, will inherit their father's estates and title.