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 novel follows the story of Genly Ai, a native of Terra, who is sent to the planet of Gethen as an envoy of the Ekumen, a loose confederation of planets. Ai's mission is to persuade the nations of Gethen to join the Ekumen, but he is stymied by his lack of understanding of Gethenian culture. Individuals on Gethen are ambisexual, with no fixed sex. This fact has a strong influence on the culture of the planet, and creates a barrier of understanding for Ai. Left Hand was among the first books in the genre now known as feminist science fiction and is the most famous examination of androgyny in science fiction. A major theme of the novel is the effect of sex and gender on culture and society, explored in particular through the relationship between Ai and Estraven, a Gethenian politician who trusts and helps him. Within that context the novel also explores the interaction between the unfolding loyalties of its main characters, the loneliness and rootlessness of Ai, and the contrast between the religions of Gethen's two major nations. The theme of gender also touched off a feminist debate when it was first published, over depictions of the ambisexual Gethenians.
The novel is part of the Hainish Cycle, a series of novels and short stories by Le Guin set in the fictional Hainish universe, which she introduced in 1964 with "The Dowry of the Angyar". Among the Hainish novels, it was preceded in the sequence of writing by City of Illusions and followed by The Word for World Is Forest.
Left Hand has been reprinted more than 30 times, and received a highly positive response from reviewers. It was voted the Hugo and Nebula Awards for Best Novel by fans and writers, respectively, and was ranked third behind Frank Herbert's Dune and Arthur C. Clarke's Childhood's End in a 1975 poll in Locus magazine. In 1987, Locus ranked it second among science fiction novels after Dune and Harold Bloom stated: "Le Guin, more than Tolkien, has raised fantasy into high literature, for our time".