Hive mind

A hive mind, (TV: Asylum of the Daleks, Death in Heaven, WC: Pond Life) group mind, gestalt consciousness or mass mind (COMIC: Culture Shock) was a collection of separate, distinct organisms with a shared consciousness, which may or may not have meant that the creatures were without individuality. (TV: Planet of the Ood)

Gestalts were creatures that together made a single entity. Axos was a "composite creature" whose individual units were different but still linked psychically. The Fendahl, however, was made up of twelve Fendahleen and the Core, with a High Priestess seeming to have control, though no clear psychic link between them. (TV: The Claws of Axos, Image of the Fendahl)

In the case of a hive mind, though, the general idea was that the same mind existed in multiple, separate beings or that each being's mind was linked with the others, allowing all organisms to know what was happening to any one organism of the hive. It was also a trait of a hive mind that each individual of the hive referred to itself as "we" or "us" rather than "I", showing that it spoke for the entire hive mind. (TV: The Impossible Planet)

Hive minds often had a shared memory. (TV: Last of the Time Lords)

The Ood were psychically linked through a hive mind (WC: Pond Life) but still retained their individualism. (TV: Planet of the Ood) Some hive minds even had leaders. The Amaryll were led by the Alvega Controller (COMIC: The Amaryll Challenge); the Rutans had a Queen (PROSE: Shakedown), as did the Wirrn. (PROSE: Placebo Effect)

Though the Daleks did not have a hive mind, the New Dalek Paradigm telepathically shared information through a pathweb. (TV: Asylum of the Daleks) Similarly, the Mondasian Cybermen at some point were all connected to a shared consciousness called the Cyberiad. (TV: Nightmare in Silver) The Cybermen created by from the corpses of the dead were connected through a hive mind too. (TV: Death in Heaven)

Because of their abilities and similarities to known hive minds, both the Vespiforms and the Hervoken may have been hive minds as well. (TV: The Unicorn and the Wasp, PROSE: Forever Autumn)

Torchwood theorised that Weevils had a low-level telepathic ability to share emotions. (TV: Combat)

The Squall were an extreme example of a gestalt consciousness; the sum intelligence of the collective Squall consciousness was distributed in small quantities. A lone Squall was barely smarter than an animal, but a whole pack was capable of speaking in full sentences and near-genius intelligence. (PROSE: Paradox Lost)

Richard Harries speculated that all beings had a collective memory that could be accessed. He experimented on rats to test this hypothesis. (PROSE: The Banquo Legacy)

The Psionovores had an undefined natural energy existence, but could coalesce into a gestalt physical form, given enough will. (AUDIO: Minuet in Hell)

An intelligence on a planet visited by the Fifth Doctor tried to lure travellers to join its gestalt, almost succeeding with Adric. (PROSE: Hearts of Stone)

At the end of the universe, the last humans on Ember attempted to transform the people of 21st century Earth into a group mind (which they called "Singularity") through the Somnus Foundation. They were defeated by the Fifth Doctor and Turlough. (AUDIO: Singularity)

The Seventh Doctor bumped into a sentient cell culture whose mass mind was able to send him a telepathic distress call. (COMIC: Culture Shock)

Known hive minds

 * The Axos (TV: The Claws of Axos)
 * The Committee (AUDIO: Spare Parts)
 * The Chronomites (GAME: TARDIS)
 * Cyberiad (TV: Nightmare in Silver)
 * The Culture (COMIC: Culture Shock)
 * The Darkness (PROSE: The Well-Mannered War)
 * The Fendahl (TV: Image of the Fendahl)
 * The Gappa (PROSE: Snowglobe 7)
 * The Isolus (TV: Fear Her)
 * The Jixen (TV: Hound of the Korven)
 * The Nestenes and Autons (TV: Spearhead from Space, Terror of the Autons, Rose)
 * The Ood (TV: Planet of the Ood)
 * The Rutans (TV: Horror of Fang Rock)
 * The Skorpius Flies (TV: Dreamland)
 * The Toclafane (TV: The Sound of Drums / Last of the Time Lords)
 * The Tractators (TV: Frontios)
 * The Vashta Nerada (TV: Silence in the Library / Forest of the Dead)
 * The Wirrn (TV: The Ark in Space)
 * The Xaranti (PROSE: Deep Blue)