Quatermass and the Pit is a British television science-fiction serial transmitted live by BBC Television in December 1958 and January 1959. It was the third and last of the BBC's Quatermass serials, although the chief character, Professor Bernard Quatermass, reappeared in a 1979 ITV production called Quatermass. Like its predecessors, Quatermass and the Pit was written by Nigel Kneale.

The serial continues the loose chronology of the Quatermass adventures. Workmen excavating a site in Knightsbridge, London, discover a strange skull and what at first appears to be an unexploded bomb. Quatermass and his newly appointed military superior at the British Rocket Group, Colonel Breen, become involved in the investigation when it becomes apparent that the object is an alien spacecraft. The ship and its contents have a powerful and malignant influence over many of those who come in contact with it, including Quatermass. He concludes that millions of years in the past the aliens, probably from Mars, had abducted pre-humans and modified them to give them psychic abilities much like their own before returning them to Earth, leaving a genetic legacy which is responsible for much of the war and racial strife in the world.

The serial has been cited as having influenced Stephen King and the film director John Carpenter. It featured in the 100 Greatest British Television Programmes compiled in 2000 by the British Film Institute, which described it as "completely gripping".