Sam Youd (16 April 1922 – 3 February 2012), known professionally as Christopher Samuel Youd, was a British writer, best known for science fiction under the pseudonym John Christopher, including the novels The Death of Grass, The Possessors, and the young-adult novel series The Tripods. He won the Guardian Prize in 1971 and the Deutscher Jugendliteraturpreis in 1976.