Here is a handy episode guide covering all 26 seasons of the original series. This guide covers TV episodes only, and does not include other media such as novels, audio dramas, comic strips, short stories, etc.
Missing Episodes:
Between 1967 and 1978, the BBC had a policy of clearing its archives by junking older episodes of shows to make room for new programs. Tapes were either burned or wiped, leading to the loss of many classics. Doctor Who was among the programs affected, with many stories from the 60s either incomplete or missing entirely.
Some episode have been found overseas and returned, including an entire copy of The Tomb Of The Cybermen, but most remain lost.
Until The Savages, each individual episode had it's own title. These stories were later given umbrella titles for the sake of clarity.
The serial Shada never completed filming and was never broadcast, but is still included in this list. The footage that was filmed was released on VHS, with Tom Baker providing narration for the missing portions.
Episodes in Seasons 1 - 21 & 23 - 26 are 25 minutes. Episodes in Season 22 are 45 minutes.
Key:
* = Incomplete story
** = All episodes missing
(#) = Number of episodes that make up the story
THE FIRST DOCTOR - WILLIAM HARTNELL
SEASON 1
(November 23, 1963 - September 12, 1964)
An Unearthly Child (4)
The Daleks (7)
The Edge Of Destrcution (2)
Marco Polo (7)**
The Keys Of Marinus (6)
The Aztects (4)
The Sensorites (6)
The Reign Of Terror (6)*
SEASON 2
(October 31, 1964 - July 24, 1965)
Planet Of Giants (3)
The Dalek Invasion Of Earth (6)
The Rescue (2)
The Romans (4)
The Web Planet (6)
The Crusade (4)*
The Space Museum (4)
The Chase (6)
The Time Meddler (4)
SEASON 3
(September 11, 1965 - July 16, 1966)
Galaxy 4 (4)**
Mission To The Unknown (1)**
The Myth Makers (4)**
The Daleks' Master Plan (12)*
The Massacre (4)**
The Ark (4)
The Celestial Toymaker (4)*
The Gunfighters (4)
The Savages (4)**
The War Machines (4)
SEASON 4
(September 10, 1966 - July 1, 1967)
The Smugglers (4)**
The Tenth Planet (4)*
THE SECOND DOCTOR - PATRICK TROUGHTON
SEASON 4 (Cont.)
The Power Of The Daleks (6)**
The Highlanders (4)**
The Underwater Menace (4)*
The Moonbase (4)*
The Macra Terror (4)**
The Faceless Ones (6)*
The Evil Of The Daleks (7)*
SEASON 5
(September 2, 1967 - June 1, 1968)
The Tomb Of The Cybermen (4)
The Abominable Snowmen (6)*
The Ice Warriors (6)*
The Enemy Of The World (6)*
The Web Of Fear (6)*
Fury From The Deep (6)**
The Wheel In Space (6)*
SEASON 6
(August 10, 1968 - June 21, 1969)
The Dominators (5)
The Mind Robber (5)
The Invasion (8)*
The Krotons (4)
The Seeds Of Death (6)
The Space Pirates (6)*
The War Games (10)