Sam Youd was a British writer best known for science fiction written under the name of John Christopher, including the novels The Death of Grass, The Possessors, and the young-adult novel series The Tripods. He won the Guardian Children's Fiction Prize in 1971 and the Deutscher Jugendliteraturpreis in 1976.

The Death of Grass is a 1956 post-apocalyptic science fiction novel written by the English author Sam Youd under the pen name John Christopher. The plot concerns a virus that kills off grass species, including rice and wheat. The Death of Grass was the first of several post-apocalyptic novels written by Youd. The novel was written in a matter of weeks and liberated him from his day job.