Walter John Herbert Sprott, known to friends as ‘Sebastian’ Sprott, and also known as Jack Sprott (1897–1971), was a British psychologist and writer.
Sprott was educated at Felsted School and Clare College, Cambridge, where he became a member of the Cambridge Apostles. In the 1920s, he became acquainted with other members of the Bloomsbury Group. He was romantically involved with the economist John Maynard Keynes, who was at the time also seeing the ballerina Lydia Lopokova. Sprott's affair with Keynes ended after Keynes married Lopokova. After a job as a demonstrator at the Psychological Laboratory in Cambridge, he moved to the University of Nottingham, where he eventually became professor of philosophy.