Gender in Doctor Who

In Doctor Who, Time Lords are canonically genderfluid, in that their genders can change between incarnations. Time Lords transform their bodies in order to prevent death, giving them a new personality each time they undergo this process. It should be noted that the new bodies that Time Lords receive after regeneration are usually not chosen intentionally. In addition to possibly changing sex when they regenerate, they may also change gender — in the words of showrunner Steven Moffat, "We must assume that gender is quite fluid on Gallifrey".

In series 10, episode 11, World Enough and Time, the Doctor explains the Time Lord attitude to gender. Less than one month after the episode aired the BBC revealed that the next incarnation of the Doctor would be played by a woman for the first time.

BILL: So, the Time Lords, bit flexible on the whole man-woman thing, then, yeah? ''DOCTOR: We're the most civilised civilisation in the universe. We're billions of years beyond your petty human obsession with gender and its associated stereotypes.''

Time Lords whose genders have changed

 * The Corsair was mentioned by the Doctor in The Doctor's Wife, season 6 episode 4, written by Neil Gaiman.
 * "Anyway, there's a living Time Lord still out there, and it's one of the good ones. ... The mark of the Corsair. Fantastic bloke. He had that snake as a tattoo in every regeneration. Didn't feel like himself unless he had the tattoo. Or herself, a couple of times. Ooo, she was a bad girl." --The Doctor, The Doctor's Wife (S06E04).
 * The Doctor is the protagonist and hero of the show, and has been played by 12 male actors. In July 2017 the BBC revealed that the thirteenth Doctor would be played by Jodie Whittaker, a woman.
 * The twelfth Doctor said about Missy, "I think she was a man back then. I'm fairly sure that I was, too. It was a long time ago, though," (S10E11) - so it would be reasonable to assume that the Doctor had been another gender than male prior to this moment.
 * The General led the Time Lord military, and has been female for most of their incarnations. In The Day of the Doctor the General is male, but dies in Hell Bent (S09E12) and regenerates into a woman and is relieved.
 * "Oh, back to normal, am I? The only time I've been a man, that last body. Dear Lord, how do you cope with all that ego?" --The General, Hell Bent (S09E12).
 * The Master is a recurring antagonist in the show, a rogue Time Lord, and the Doctor's nemesis. They have been played by seven men and most recently one woman.