Robert Anson Heinlein was an American science fiction writer. Often called "the dean of science fiction writers", he was one of the most popular, influential, and controversial authors of the genre. He set a high standard for science and engineering plausibility and helped to raise the genre's standards of literary quality. He was one of the first writers to break into mainstream, general magazines such as The Saturday Evening Post, in the late 1940s, with unvarnished science fiction.

He was among the first authors of bestselling, novel-length science fiction in the modern, mass-market era. For many years, Heinlein, Isaac Asimov, and Arthur C. Clarke were known as the "Big Three" of science fiction. Notable works include Stranger in a Strange Land, Starship Troopers, and The Moon Is a Harsh Mistress. His work sometimes had controversial aspects, such as plural marriage in The Moon Is a Harsh Mistress and militarism in Starship Troopers. His technologically competent women characters were formidable, yet often stereotypically feminine, such as in Friday.

Heinlein used his science fiction as a way to explore provocative social and political ideas and to speculate on how progress in science and engineering might shape the future of politics, race, religion, and sex. Within his stories, Heinlein addressed social themes such as the importance of individual liberty and self-reliance, the nature of sexual relationships, and the influence of organized religion on culture and government.

Heinlein was named the first Science Fiction Writers Grand Master in 1974. Four of his novels won Hugo Awards, and he was awarded "Retro Hugos" for several works published before the Hugo Awards came into existence. In his fiction, he coined terms that have become part of the English language, including grok, waldo, and speculative fiction. His influence on the science-fiction genre and modern culture continues to be significant.