Andromeda (galaxy)

The Andromeda Galaxy, also known as M31, was a galaxy located near the Milky Way, about 2.6 million light years from Earth.

History
Mavic Chen, Guardian of the Solar System, attended the Intergalactic Conference of Andromeda some time prior to 4000. Planktus of the Outer Galaxies also attended. (TV: The Daleks' Master Plan)

Humans reached the Andromeda Galaxy by the time of Space Station Nerva's conversion into a space ark. The Wirrn were native to Andromeda, their breeding colonies were destroyed by human colonists and, after a thousand years of fighting, they were driven from the Galaxy. They came to call Andromeda "the old lands". (TV: The Ark in Space) The Wirrn devastated the Phylox system. (PROSE: Placebo Effect)

A hundred million years after humans visited the Andromeda Galaxy, the First Doctor's TARDIS landed in a planetoid-sized ship and an armada of smaller ships, travelling slower than the speed of light headed for Mutter's Spiral in order to conquer it. The ship contained the One, made up of millions of Andromedan minds, life forms from the Andromeda Galaxy and Aalas, the android servants of the One. (PROSE: Doctor Who and the Invasion from Space)

At some point, there were high tensions between the organic and mechanical lifeforms in the Andromeda Galaxy, exemplified by the rise of the Cult of Shining Darkness. Andromeda was home to Near-humans as well as several nonhumanoid forms. The Doctor considered his knowledge of Andromeda to be spotty. (PROSE: Shining Darkness)

Behind the scenes

 * According to background information given in FASA's The Doctor Who Role Playing Game, the android Movellans originated in Andromeda before being expelled from that galaxy by a coalition of races known as the Organic League.