Tor Books is the primary imprint of Tor Publishing Group (previously Tom Doherty Associates), a publishing company based in New York City. It primarily publishes science fiction and fantasy titles.

Tor was founded by Tom Doherty in 1980, with Harriet McDougal and Jim Baen joining him from Ace as the editorial staff. (Baen and Doherty founded Baen Books three years later.) They were soon joined by Barbara Doherty and Katherine Pendill, who then composed the original startup team.

Tor is a word meaning a rocky pinnacle, as depicted in Tor's logo. Tor Books was sold to St. Martin's Press in 1987. Along with St. Martin's Press; Henry Holt; and Farrar, Straus and Giroux, it became part of the Holtzbrinck group, now part of Macmillan in the US.

In June 2019, Tor and other Macmillan imprints moved from the Flatiron Building, to larger offices in the Equitable Building.

Tor is the primary imprint of Tor Publishing Group. The Forge imprint publishes an array of fictional titles, including historical novels and thrillers. The Nightfire imprint publishes horror, largely but not exclusively with science fiction and fantasy elements. The Bramble imprint publishes romance and romantic stories with elements of other genres. Tor Books has two imprints for young readers: Starscape (for readers 10 years of age and up) and Tor Teen (for readers 13 years of age and up). The Tordotcom imprint focuses on short works such as novellas, shorter novels and serializations.

A United Kingdom sister imprint, Tor UK, specializes in science fiction, fantasy, and horror, and publishes young-adult crossover fiction based on computer-game franchises. Tor UK briefly maintained an open submission policy, which ended in January 2013.

Orb Books publishes science-fiction classics such as A. E. van Vogt's Slan.

Tor Teen publishes young-adult novels such as Cory Doctorow's Little Brother and repackages novels such as Orson Scott Card's Ender's Game for younger readers.