1966 (releases)


 * 1 January - "Volcano" debuted on BBC1.
 * 8 January - "Golden Death" debuted on BBC1.
 * 15 January - "Escape Switch" debuted on BBC1.
 * 12 February - The final part of COMIC: The Didus Expedition was released.
 * 22 January - "The Abandoned Planet" debuted on BBC1.
 * 22 - The first part of COMIC: The Didus Expedition was released.
 * 29 January - "Destruction of Time" debuted on BBC1. Jean Marsh left the series as her character, Sara Kingdom, became the second companion to die in the line of duty.
 * 30 January - Actor Daphne Ashbrook was born.
 * 5 February - "War of God" debuted on BBC1.
 * 12 February - "The Sea Beggar" debuted on BBC1.
 * 19 February - "Priest of Death" debuted on BBC1.
 * 19 - The first part of COMIC: Space Station Z-7 was released.
 * 26 February - "Bell of Doom" debuted on BBC1. Jackie Lane made her debut as companion Dodo Chaplet.

Early 1966

 * Exact date unknown - William Hartnell sent shockwaves through the Doctor Who production team by announcing his intention to leave the series. Over the following months, producers and writers developed the concept of regeneration to explain the change of lead actor and cast Patrick Troughton as the new Doctor; Hartnell eventually agreed to appear in the first two serials of the new season.
 * Dalek Action Paint 'n Puzzle was published by Souvenir Press.
 * Dr. Who Travels in Space Sticker Fun Book was published.
 * Dr. Who Travels in Time Sticker Fun Book was published.
 * 5 March - "The Steel Sky" debuted on BBC1.
 * 12 March - "The Plague" debuted on BBC1.
 * 12 - The final part of COMIC: The Didus Expedition was released.
 * 19 March - "The Return" debuted on BBC1.
 * 19 - The first part of COMIC: Plague of the Black Scorpi was released.
 * 26 March - "The Bomb" debuted on BBC1.
 * Century 21 Records released a Doctor Who edition of its 21 Minutes of Adventure LP record series, featuring the audio soundtrack of "The Planet of Decision", a chapter of The Chase. It was the first audio story to be made available for sale.
 * 2 April - "The Celestial Toyroom" debuted on BBC1.
 * 9 April - "The Hall of Dolls" debuted on BBC1.
 * 09 - The final part of COMIC: Plague of the Black Scorpi was released.
 * 16 April - "The Dancing Floor" debuted on BBC1.
 * 23 April - "The Final Test" debuted on BBC1.
 * 30 April - "A Holiday for the Doctor" debuted on BBC1.
 * The Doctor Who production office circulated a memo to writers outlining the proposed character of the Second Doctor, as well as suggestions on handling the first regeneration, which was initially compared to an LSD trip gone bad.
 * 7 May - "Don't Shoot the Pianist" debuted on BBC1.
 * 14 May - "Johnny Ringo" debuted on BBC1.
 * 20 May - Mervyn Pinfield, a director and associate producer for Doctor Who, died.
 * 21 May - "The OK Corral" debuted on BBC1. This marked the final time individual episode titles would be used in the original series (the practice would resume in 2005).
 * 28 May - The Savages Episode 1 was first broadcast.
 * 4 June - The Savages Episode 2 was first broadcast.
 * 11 June - The Savages Episode 3 was first broadcast.
 * 18 June - The Savages Episode 4 was first broadcast. Peter Purves left the series with this episode, although he would continue his association with Doctor Who for years to come when he subsequently became co-host of Blue Peter, often presenting promotional features about the series.
 * 19 June - Actor Samuel West was born.
 * 25 June - The War Machines Episode 1 was first broadcast. Michael Craze and Anneke Wills made their debuts as Ben Jackson and Polly, respectively. This episode was notorious for having a character -- the computer WOTAN -- break the longstanding taboo of referring to the Doctor as "Doctor Who".
 * 2 July - The War Machines episode 2 was first broadcast. This was the final appearance of Jackie Lane as Dodo Chaplet.
 * 9 July - The War Machines Episode 3 was first broadcast.
 * 16 July - The War Machines Episode 4 was first broadcast, concluding the third season.
 * The film Dr. Who and the Daleks was released to theatres in the United States. For most audiences in America, this was their first exposure to the Doctor Who concept, as the TV series had not as of this date been broadcast in the US (although some communities bordering Canada were able to view the series on the CBC network).
 * 30 July - Actor Jason Watkins was born.
 * 5 August - The second feature film, Daleks' Invasion Earth 2150 A.D., based upon The Dalek Invasion of Earth, was released in the UK.
 * The second Doctor Who Annual was published.
 * 8 September - The Dalek Outer Space Book was first published.
 * 08 - Star Trek debuted in America. This influential series became Doctor Who's chief rival in terms of franchise longevity, although the original series only ran until the spring of 1969.
 * 10 September - The Smugglers Episode 1 was first broadcast, marking the beginning of Season 4.
 * 17 September - The Smugglers Episode 2 was first broadcast.
 * 24 September - The Smugglers Episode 3 was first broadcast.
 * 1 October - The Smugglers Episode 4 was first broadcast.
 * 8 October - The Tenth Planet Episode 1 was first broadcast, marking the first appearance of the Cybermen.
 * 08 - Episode 4 of The Tenth Planet was taped, with the first scenes filmed being the regeneration from William Hartnell (making his final regular appearance as the First Doctor) to Patrick Troughton (making his first appearance as the Second Doctor).
 * 15 October - The Tenth Planet Episode 2 was first broadcast.
 * 17 October - Actor Mark Gatiss was born.
 * 22 October - The Tenth Planet Episode 3 was first broadcast.
 * 22 - Episode 1 of The Power of the Daleks was taped; this was the first full episode featuring Patrick Troughton.
 * 29 October - The Tenth Planet Episode 4 was first broadcast, ending in the first regeneration, from William Hartnell to Patrick Troughton, shocking children across Britain.
 * 5 November - The Power of the Daleks Episode 1 was first broadcast. This was Patrick Troughton's first full episode as the Second Doctor, although William Hartnell briefly appears as a mirror reflection.
 * 12 November - The Power of the Daleks Episode 2 was first broadcast.
 * 19 November - The Power of the Daleks Episode 3 was first broadcast.
 * 22 November - Actor Nicholas Rowe was born.
 * 26 November - The Power of the Daleks Episode 4 was first broadcast.
 * 3 December - The Power of the Daleks Episode 5 was first broadcast.
 * 10 December - The Power of the Daleks Episode 6 was first broadcast.
 * 12 December - The BBC Audience Research Dept. filed an Audience Research Report on The Power of the Daleks Episode 3, reporting that satisfaction in the episode ranked at 44% with response to new Doctor Patrick Troughton being particularly mixed.
 * 15 December - Patrick Troughton was interviewed in Radio Times.
 * 17 December - The Highlanders Episode 1 was first broadcast. Frazer Hines debuted as new companion Jamie McCrimmon.
 * 24 December - The Highlanders Episode 2 was first broadcast.
 * 31 December - The Highlanders Episode 3 was first broadcast.

Unknown dates

 * Doctor Who and the Invasion from Space was published by World Distributors. A hardcover novella, this was the first publication of an original long-form text story to feature the First Doctor. (It was presumably published prior to October as it featured the First Doctor.)
 * US comic book publisher Dell Comics issued a single-issue adaptation of the Dr. Who and the Daleks film. This was the first (and, until the early 1980s, only) appearance of a Doctor Who-related comic book in the US.