Z.P.G. (short for "Zero Population Growth") is a 1972 British dystopian science fiction film starring Oliver Reed and Geraldine Chaplin and directed by Michael Campus. It is inspired by the non-fiction best-selling book The Population Bomb by Paul R. Ehrlich. The film concerns an overpopulated, very polluted future Earth, whose world government executes those who violate a 30-year ban on having children.