The Left Hand of Darkness is a science fiction novel by U.S. writer Ursula K. Le Guin, published in 1969. The novel became immensely popular and established Le Guin's status as a major author of science fiction. The book is a part of the Hainish Cycle, a series of novels by Le Guin, all set in the same universe, where the people of different planets are attempting to co-operate with one another. The novel follows the story of Genly Ai, a human native of Terra, who is sent to the planet Gethen as an envoy of the Ekumen, a loose group of planets. Ai's mission is to persuade the nations of Gethen to join the Ekumen, but he is hindered by lack of understanding of Gethenian culture. Individuals on Gethen are ambisexual, with no fixed sex, which is a central theme in the novel.