The Web of Fear is the partly missing fifth serial of the fifth season of the British science fiction television series Doctor Who, which was first broadcast in six weekly parts from 3 February to 9 March 1968.

The serial is set on the London Underground railway over forty years after the 1967 serial The Abominable Snowmen. In the serial, the incorporeal Great Intelligence leads the time traveller the Second Doctor (Patrick Troughton) into a trap where it can drain the Doctor's mind of all of his knowledge. This serial marked the last regular appearance of the Yeti, although they would return for small cameos in The Five Doctors and the Reeltime Pictures spin-off Downtime.

The Web of Fear marks the first appearance of actor Nicholas Courtney as Colonel Alistair Lethbridge-Stewart, subsequently better known as the Brigadier, and acts as a precursor to the numerous later serials involving the UNIT organisation.

Only five of the six episodes are held in the BBC Archives; one still remains missing.

For decades, all but episode 1 were thought to have been destroyed, but on 11 October 2013, the BBC announced the previously missing episodes 2 and 4-6 were recovered from Nigeria. Episode 3, however, was reportedly stolen by a private collector on its way back to the UK, so an animated reconstruction had to be made for episode 3. On 16 August 2021, a special edition Blu-ray and DVD release of the serial saw the missing episode reconstructed using 3D motion capture animation, a first for missing episodes.