1975

According to Mary, 1975 was the year Toshiko Sato was born. (TV: Greeks Bearing Gifts)

On 24 December, the Seventh Doctor and his companions Ace and Hex defeated the Kellenian invasion of Earth in New York City. (PROSE: Presence)

January to April

 * The stage play Doctor Who and the Daleks in The Seven Keys to Doomsday toured the UK.

January

 * PROSE: Doctor Who and the Curse of Peladon was first published.
 * 1 - Actress Andrea Lowe was born.
 * 4 - TV: Robot Episode 2 was first broadcast.
 * 11 - TV: Robot Episode 3 was first broadcast.
 * 16 - The BBC's Audience Research Dept. filed an Audience Research Report on TV: Robot Episode 1. The episode received a Reaction Index of 53. Reaction to new Doctor Tom Baker was mixed, with some respondents saying he would take some getting used to.
 * 18 - TV: Robot Episode 4 was first broadcast. Although there were two more UNIT stories over the next year, this episode marked the end of the Doctor's continuous involvement with UNIT.
 * 24 - Actor Neil Wilson died.
 * 25 - TV: The Ark in Space Episode 1 was first broadcast.

February

 * 01 - TV: The Ark in Space Episode 2 was first broadcast.
 * 06 - Actor Nabil Elouahabi was born.
 * 08 - TV: The Ark in Space Episode 3 was first broadcast.
 * 15 - TV: The Ark in Space Episode 4 was first broadcast.
 * 20 - PROSE: Doctor Who and the Cybermen was first published.
 * 22 - TV: The Sontaran Experiment Episode 1 was first broadcast.
 * 22 - Writer Peter R. Newman died.

March

 * 01 - TV: The Sontaran Experiment Episode 2 was first broadcast.
 * 08 - TV: Genesis of the Daleks Episode 1 was first broadcast. This was the first appearance of Davros.
 * 10 - Actor Yee Jee Tso was born.
 * 13 - PROSE: Doctor Who and the Giant Robot was first published. It was the first novelisation of a Fourth Doctor serial and the first novelisation to be published during the same TV season in which the adapted serial (TV: Robot) was actually broadcast.
 * 15 - TV: Genesis of the Daleks Episode 2 was first broadcast.
 * 22 - TV: Genesis of the Daleks Episode 3 was first broadcast.
 * 29 - TV: Genesis of the Daleks Episode 4 was first broadcast.

April

 * 05 - TV: Genesis of the Daleks Episode 5 was first broadcast.
 * 12 - TV: Genesis of the Daleks Episode 6 was first broadcast.
 * 19 - TV: Revenge of the Cybermen Episode 1 was first broadcast.
 * 23 - Actor William Hartnell died in Marden, Kent, England. Hartnell has the sad distinction of being the first major, ongoing cast member of Doctor Who to pass away.
 * 26 - TV: Revenge of the Cybermen Episode 2 was first broadcast.
 * 26 - Actor Kevin Lindsay died.

May

 * 03 - TV: Revenge of the Cybermen Episode 3 was first broadcast.
 * 10 - TV: Revenge of the Cybermen Episode 4 was first broadcast, bringing Season 12 to a premature end following the BBC's decision to reschedule the originally planned season finale, TV: Terror of the Zygons, to the start of Season 13.
 * 15 - PROSE: Doctor Who and the Terror of the Autons was first published.
 * 24 - Actor William Sasso was born.

June

 * 16 - Actor Fred Koehler was born.

July

 * 15 - Actor Raf De La Torre died.

August

 * 21 - PROSE: Doctor Who and the Green Death was first published.
 * 23 - Tom Baker presented Disney Time in character as the Fourth Doctor
 * 30 - TV: Terror of the Zygons Episode 1 was first broadcast, opening Season 13 and marking the first autumn start for a Doctor Who season since 1968-69. The serial was originally intended to end Season 12, but was pushed back to make a fall season start feasible.

September

 * Doctor Who Annual 1976 was published.
 * Terry Nation's Dalek Annual 1976 was published
 * 06 - TV: Terror of the Zygons Episode 2 was first broadcast.
 * 13 - TV: Terror of the Zygons Episode 3 was first broadcast.
 * 20 - TV: Terror of the Zygons Episode 4 was first broadcast. Ian Marter left the series as a regular with this episode, although he returned a few weeks later for a guest appearance in TV: The Android Invasion. This was also Nicholas Courtney's final regular appearance as Brigadier Alistair Gordon Lethbridge-Stewart; he next played the character in the 1983 serial TV: Mawdryn Undead. Although UNIT returned in The Android Invasion and the Doctor was on a UNIT mission in TV: The Seeds of Doom, this was the last appearance of the Brigadier and marked as the official end of the UNIT era.
 * 24 - Actor Clive Morton died.
 * 27 - TV: Planet of Evil Episode 1 was first broadcast.

October

 * 04 - TV: Planet of Evil Episode 2 was first broadcast.
 * 11 - TV: Planet of Evil Episode 3 was first broadcast.
 * 16 - PROSE: Doctor Who and the Planet of the Spiders was first published.
 * 18 - TV: Planet of Evil Episode 4 was first broadcast.
 * 24 - Actor Martin Boddey died.
 * 25 - TV: Pyramids of Mars Episode 1 was first broadcast.

November

 * 01 - TV: Pyramids of Mars Episode 2 was first broadcast.
 * 08 - TV: Pyramids of Mars Episode 3 was first broadcast.
 * 15 - TV: Pyramids of Mars Episode 4 was first broadcast.
 * 20 - PROSE: Doctor Who - The Three Doctors was first published. It was the first novelisation not to use the title form Doctor Who and the .... This was also the first Target Books-commissioned novelisation to feature the First Doctor.
 * 20 - The Doctor Who Monster Book was first published.
 * 22 - TV: The Android Invasion Episode 1 was first broadcast.
 * 29 - TV: The Android Invasion Episode 2 was first broadcast.

December

 * 06 - TV: The Android Invasion Episode 3 was first broadcast.
 * 06 - Actor Noel Clarke was born.
 * 13 - TV: The Android Invasion Episode 4 was first broadcast. It was the final appearances of Ian Marter as Harry Sullivan, John Levene as John Benton and, as a regular part of the series, UNIT. After this episode the series went on a brief hiatus for Christmas.

Unknown

 * Actor Dean Lennox Kelly was born.