The black and white story sees Patrick Troughton's second Doctor battle robot yeti in the London Underground.
Also recovered is a complete version of Troughton's six-part story The Enemy of the World.
It is thought to be the largest haul of missing episodes recovered in the last three decades.
"It's thrilling," said Mark Gatiss, an actor and writer for the 21st Century incarnation of Doctor Who.
"Every single avenue seemed to have been exhausted, every now and then something turns up - but to have two virtually complete stories out of the blue is absolutely incredible."
The BBC destroyed many of the sci-fi drama's original transmission tapes in the 1960s and 1970s.
However, many episodes were transferred on to film for sale to foreign broadcasters. It is often these prints found in other countries that are the source of retrieved episodes.
In this case, 11 Doctor Who episodes were discovered, nine of which were missing, in the Nigerian city of Jos.
The Enemy of the World (1967-68) - episodes 1,2,3,4,5,6 (episode 3 was already in archive)
The Web of Fear (1968) - episodes 1,2,4,5,6 (episode 1 was already in archive - episode 3 still missing)
Full Article @ BBC