Several portions of the long-running British science-fiction television programme Doctor Who are no longer held by the BBC. Between 1967 and 1978, the BBC routinely deleted archive programmes for various practical reasons—lack of space, scarcity of materials, and a lack of rebroadcast rights. As a result, 97 of 253 episodes from the programme's first six years are currently missing, primarily from seasons 3, 4 and 5, leaving 26 serials incomplete. Many more were considered lost until recovered from various sources, mostly overseas broadcasters.

Doctor Who is not unique in its losses, as many broadcasters routinely cleared their archives in this manner. Until the BBC changed its archiving policy in 1978, thousands of hours of programming in all genres were deleted. Other affected BBC series include Hancock's Half Hour, Dad's Army, Z-Cars, The Likely Lads, The Wednesday Play, Till Death Us Do Part, Steptoe and Son, Dixon of Dock Green and Not Only... But Also. ITV regional franchisees, such as Rediffusion Television and Associated Television, also deleted many programmes, including early videotaped episodes of The Avengers.

Doctor Who is unusual in that each of its 97 missing episodes survives in audio form, recorded off-air by fans at home. Most episodes are also represented by production stills, tele-snaps, or short video clips. Furthermore, after careful restoration, all 1970s episodes are available in full colour.

Efforts to locate the missing episodes have continued, both by the BBC and by fans of the series. The recovered episodes have been extensively restored for release on VHS and DVD; surviving soundtracks have been released on cassette and compact disc. Many missing episodes have had their visuals reconstructed, either through specially commissioned animation or use of surviving footage and photographs.

Between approximately 1967 and 1978, large quantities of videotape and film stored in the BBC's Engineering department and film libraries were wiped or destroyed to make way for newer programmes. This happened for several reasons, primarily the belief that there was no practical value to its retention.

The actors' union Equity had actively fought against the introduction of TV recording since the 1950s, when it first became a practical proposition. Before workable television recording was developed, if a broadcaster wished to repeat a programme (usually a one-off play), they had to re-hire the actors to perform it again, live, for additional fees. Equity's concern was that if broadcasters kept recordings of the original performances, they would be able to re-broadcast them indefinitely, which would reduce the amount of new production and threaten the livelihoods of its members. Although Equity could not prevent recording altogether, it added standard clauses to its members' contracts that stipulated that recordings could only be repeated a limited number of times within a specific timeframe, and deliberately set the fees for further use so high that broadcasters would consider it unjustifiable to spend so much money repeating an old programme rather than making a new one. Consequently, recordings whose repeat rights had expired were considered to be of no further domestic use to the broadcasters.

Most Doctor Who episodes were made on two-inch videotape for initial broadcast and then telerecorded onto 16 mm film by BBC Enterprises for further commercial use. Enterprises used 16 mm for overseas sales as it was considerably cheaper to buy and easier to transport than videotape. It also circumvented the problem of different countries' incompatible video standards, as film was a universal medium whereas videotape was not. The BBC had no central archive at the time; the Film Library kept programmes that had been made on film, while the Engineering Department was responsible for storing videotapes. BBC Enterprises only kept copies of programmes that they deemed commercially valuable. They had little dedicated storage space, and tended to place piles of film canisters wherever they could find space for them at their Villiers House property.

The Engineering Department had no mandate to archive the programme videotapes they held, although typically they would not be wiped or junked until the relevant production department or BBC Enterprises indicated that they had no further use for the tapes. The first Doctor Who master videotapes to be wiped were those for the serial The Highlanders, which were erased on 9 March 1967, a mere two months after Episode 4's original transmission. Episode seven of The Daleks' Master Plan was cleared for wiping on 17 August 1967; it is considered the first Doctor Who episode to be permanently lost, as no telerecordings of that episode were ever made. Further erasing of Doctor Who master videotapes by the Engineering Department continued into the 1970s. Eventually, every master videotape of the programme's first 253 episodes (1963–69) was destroyed or wiped. The final 1960s master tapes to be erased were those for the 1968 serial Fury from the Deep, in late 1974.^{[better source needed]}