The Ark is the sixth serial of the third season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts from 5 to 26 March 1966.

The last two episodes are set 700 years later, and involve the Doctor, Steven and Dodo working with the Refusian race to stop the Monoids from wiping out the last of humanity with a bomb.

The ship is commanded by human Guardians, while menial work is undertaken by a race of mute, one-eyed non-humans called Monoids.

They discover that the Monoids have taken control of the ship, enabled by electronic voice communicators, while the human descendants, genetically weakened by the cold virus, are now slaves.

As the Ark arrives at its destination, the Monoid leader assembles a landing party to Refusis II with the Doctor, Dodo and a human, Yendom.

They discover a large building amid the vegetation, occupied by the Refusians, giant beings rendered invisible by solar flares.

Steven leads the humans in an escape from the Ark, and they travel to the planet in landing pods, where they discover the Monoids engaged in a civil war.

The concept of an interstellar ark ship was devised by producer John Wiles, and script editor Donald Tosh collaborated with Paul Erickson, the programme's new screenwriter.

The serial's title comes from an explicit reference in "The Steel Sky", in which Dodo Chaplet remarks that the spaceship carrying Earth's animals and humans to safety is similar to the Biblical narrative of Noah's Ark.

[citation needed] Reviewing the serial in 2009, Patrick Mulkern of Radio Times stated, "The concept is fine, especially with the time-lapse cliffhanger to episode two ...

[12] Arnold T. Blumberg of IGN rated the serial an eight out of ten, highlighting the "snappy and exciting" pace and the "surprisingly top-notch" production values, aside from the Monoids.

[16] Reflecting on the apocalyptic themes of The Ark, Andrew Crome links the complexities of human-Monoid integration with contemporary debates around the Race Relations Act 1965, and notes that, while the Doctor accepts the servitude of the Monoids without challenge, he is keen to encourage revolt to free the humans.