"They" is a short story written by American science fiction author Robert A. Heinlein. It was first published in the April 1941 issue of Unknown, and can be found in Heinlein's short story collection The Unpleasant Profession of Jonathan Hoag. It also appears in a number of multi-author anthologies.
The story concerns a man who is confined to a mental institution because he is suffering from the delusion that he is one of the few "real" entities in the universe, and that the other "real" entities have created the rest of the universe in a conspiracy to deceive him. He spends much of the story engaged in verbal sparring with the psychiatrist who is caring for him, and in pondering his predicament, trying to figure out a way to prove that his belief is true. On the final page of the story, the reader discovers that his belief is true; the god-like character "the Glaroon" is behind the conspiracy. However, this revelation is kept from the protagonist.
The delusion described above is similar to the philosophical tenet known as solipsism, the principal difference being that the protagonist in the short story acknowledged that he was not the only entity in existence. Heinlein explored ideas centered on pantheistic solipsism and the nature of reality in a number of his other works, including the short story "All You Zombies—", and the novel Number of the Beast.
There is a small connection to Heinlein's later novel, Job: A Comedy of Justice. "The Glaroon" reappears as a minor god.
This is a non-comprehensive list of short stories with significant science fiction elements.