The Cybermen are a fictional race of cyborgs principally portrayed in the British science fiction television programme Doctor Who. The Cybermen are a species of space-faring cyborgs who often forcefully and painfully convert human beings (or other similar species) into more Cybermen in order to populate their ranks while also removing their emotions and personalities. They were conceived by writer Kit Pedler (who was also the unofficial scientific advisor to the series) and story editor Gerry Davis, and first appeared in the 1966 Doctor Who serial The Tenth Planet.

The Cybermen have seen many redesigns and costume changes over Doctor Who's long run, as well as a number of varying origin stories. In their first appearance, The Tenth Planet (1966), they are humans from Earth's nearly identical "twin planet" of Mondas who upgraded themselves into cyborgs in a bid for self-preservation. Forty years later, the two-part story, "Rise of the Cybermen" and "The Age of Steel" (2006), depicted Cybermen invented again in a parallel universe London as a business corporation's attempt at upgrading humanity. Doctor Who audio dramas, novels, and comic books have also elaborated on existing origin stories or presented alternatives. The 2017 episode, "The Doctor Falls", explains the different origins as parallel evolution, due to the inevitability of humans and human-like species upgrading themselves through technology; this perspective resolves continuity differences in the Cybermen's history.

A mainstay of Doctor Who since the 1960s, the Cybermen have also appeared in related programmes and spin-off media, including novels, audiobooks, comic books, and video games. Cybermen stories were produced in officially licensed Doctor Who products between 1989 and 2005, when the TV show was off the air, with writers either filling historical gaps or depicting new encounters between them and the Doctor. The species also appeared in the Doctor Who TV spin-off, Torchwood, appearing in the fourth episode, "Cyberwoman" (2006).

The name "Cyberman" comes from cybernetics, a term used in Norbert Wiener's book Cybernetics or Control and Communication in the Animal and the Machine (MIT Press, 1948). Wiener used the term in reference to the control of complex systems, particularly self-regulating control systems, in the animal world and in mechanical networks. By 1960, doctors were researching surgical or mechanical augmentation of humans and animals to operate machinery in space, leading to the portmanteau "cyborg", for "cybernetic organism".

In the 1960s, "spare-part" surgery began with the development of gigantic heart-lung machines. Public discussion included the possibility of wiring amputees' nerve endings directly into machines. In 1963, Kit Pedler discussed with his wife (who was also a doctor) what would happen if a person had so many prostheses that they could no longer distinguish themselves between man and machine. He got the opportunity to develop this idea when, in 1966, after an appearance on the BBC science programmes Tomorrow's World and Horizon, the BBC hired him to consult on the Doctor Who serial The War Machines (1966). That eventually led to him writing, with Gerry Davis, The Tenth Planet (1966) for Doctor Who.

Pedler, influenced by the logic-driven Treens from the Dan Dare comic strip, originally envisaged the Cybermen as "space monks", but was persuaded by Davis to concentrate on his fears about the direction of spare-part surgery. The Cybermen were originally imagined as human but with plastic and metal prostheses. The Cybermen of The Tenth Planet still have human hands, and their facial structures are visible beneath the masks they wear, but over time they evolved into metallic, more fully mechanized designs.

A variety of specialized forms of Cybermen have been shown, in particular Cyber Leaders and Cyber Controllers, with power to command other Cybermen.

The Cybermen first appear in the serial The Tenth Planet in 1966, set in 1986. This story explains how, millions of years ago, Earth had a twin planet known as Mondas that was knocked out of solar orbit and drifted into deep space. The Mondasians, already far in advance of Earth's technology and fearful for their race's survival, replaced most of their bodies with cybernetic parts. Having eventually removed all emotion from their brains (to maintain their sanity), the natives installed a drive propulsion system to pilot the planet itself through space. As the original race was limited in numbers and were continually being depleted, the Mondasians – now Cybermen – became a race of conquerors who reproduced by forcibly changing other organic beings into Cybermen. The First Doctor (William Hartnell) opposes these Cybermen when they attempt to drain the Earth's energy to make way for Mondas' return to the Solar System; in this encounter, Mondas absorbs too much energy from Earth, destroying it and all Cybermen on Earth. The adventure takes its physical toll on the Doctor, forcing him to regenerate for the first time, becoming the Second Doctor (Patrick Troughton).