Walter William Rouse Ball (14 August 1850 — 4 April 1925) was a British mathematician, lawyer and a fellow at Trinity College, Cambridge from 1878 to 1905. He was also a keen amateur magician, and the founding president of the Cambridge Pentacle Club in 1919, one of the world's oldest such societies.
Walter William Rouse Ball was the son and heir of Walter Frederick, of 3, St John's Park Villas, South Hampstead, London. Educated at University College School, he entered Trinity College, Cambridge in 1870, became a scholar and first Smith's Prizeman, and gained his BA in 1874 as second University. He became a Fellow of Trinity in 1875, and remained one for the rest of his life.
He is buried at the Parish of the Ascension Burial Ground in Cambridge.