"Critical Mass" is a science fiction novelette by American writers Frederik Pohl and Cyril M. Kornbluth. It was first published in "Galaxy Science Fiction" magazine in February 1962, almost four years after Kornbluth's death. According to a foreword by Pohl in a collection also called "Critical Mass", the story was assembled from notes Kornbluth made for three story ideas, plus one of Pohl's own from 1954. After Kornbluth's death, his widow turned over his story notes and drafts to Pohl. Pohl completed a dozen or so stories based on this material, most of which were eventually collected in the volume "The Wonder Effect" which contained most of the same stories as the later "Critical Mass" collection.