Sir Francis Drake: Well, I started growing breasts when I was thirteen and then...
Rin: Not remotely what I meant!
In-Universe explanations for this vary. Sometimes "Alice" disguised herself as "Aleister" or vice versa, sometimes the details were lost over time or covered up for political reasons, and sometimes it's just an Alternate Universe where the figure is replaced by a Distaff Counterpart or Spear Counterpart. Urban Fantasy has its own variant where history is unaltered, but the character is Reincarnated in the modern day as the opposite sex.
Can be used to "spice up" a historical tale with new possibilities for character relationships, extra challenges for the protagonist to overcome... or just Fanservice. It can also happen as a side-effect of combining the roles of two or more people together. In extreme cases just about everyone in the story is like this, usually for the sake of creating an Improbably Female Cast.
This is a Sub-Trope of Historical Domain Character and Gender Flip. Frequently overlaps with Beethoven Was an Alien Spy, Historical Beauty Update (due to Attractive Bent-Gender) and She Is the King. Not to be confused with Cross-Cast Role.
- Bungo Stray Dogs has several male writers in real life portrayed as girls/women.
- Classicaloid, a comedy series about reincarnating famous composers into new bodies, genderbends Franz Liszt and Pyotr Ilyich Tchaikovsky into a mature woman and teenage girl respectively. Liszt doesn't seem to mind this change and indulges in Fanservice, while Tchaiko absolutely hates it - often reverting into a "old man" personality.
- Code Geass goes for the Distaff Counterpart route with Nina Einstein, though it's not obvious for a while - she invents an atomic bomb, which is basically The Theme Park Version of Albert Einstein's accomplishments.
- Ikki Tousen is a retelling of Romance of the Three Kingdoms which falls somewhere between Reincarnation and Generation Xerox.
- Ikaros Publishing released in 2012 the controversial artwork Nyotaika!! Dictator Biographies in the World, which represents infamous dictators from 20th century as cute and/or sexy girls accompanied with their biographies.
- This is the entire point of Ooku, a historical alternate universe where an even-more virulent version of smallpox kills practically every man in seventeenth-century Japan and various historical figures are replaced by female versions. This tendency carries on well into the 19th century after the pox is eradicated by a vaccine.
- Sengoku Otome is set in an Alternate Universe Jidaigeki where all the notable figures exist but there are no men.
- A manga called Shiroi Majo was released in 2014 which features Simo Häyhä in the middle of the Winter War in 1939. Just one slight difference from reality: "Simo Häyhä" is a teenage girl who looks outrageously similar to Sinon.
- Strike Witches is an Alternate Universe version of World War II, with the protagonists taking names and traits from (mostly male) Ace Pilots.
- In UQ Holder!, Karin is actually a gender flipped version of Judas Iscariot, Jesus' betrayer.
- An In-Universe example happens in Yona of the Dawn, in which Hiryuu, the legendary first king of Kouka, reincarnated into the young princess Yona that changed her from a Royal Brat into a Royal Who Actually Does Something during the series to the point of starting her own revolution to get her kingdom back as Hiryuu did once.
- Fate/Gamers Only: Lampshaded when Rikku meets the female Francis Drake as the third gender flip she's met after Artoria (King Arthur) and Altera (Attila the Hun).
Rikku: "At this point, I am convinced that there's some kind of malicious entity that is intentionally reaching back in time and genderbending historical figures for it's own amusement."
- Fate/Harem Antics:
- In addition to the many canon Nasuverse examples, there is a very strange version with Shielder. She is a woman, but is soon revealed to be Sir Galahad, one of King Arthur's most famous knights. The odd part is that in Fate/Grand Order, Shielder is Mash Kyrielight (female), an artificial Servant borrowing the powers and legends of Sir Galahad (male). In this fic, the two are combined so that Galahad was always female, and has Mash's appearance and personality. King Arthur recognizes her on sight, so it's definitely not one of the oddities of the Grail.
- King Arthur herself is a woman and comments she hid her gender in life, so she's not particularly surprised that historians never discovered the truth.
- As in canon, Sir Francis Drake is female here, and Rin lampshades the absurdity of it. In particular, Drake was married twice; how did she keep her gender hidden from her wives? Drake smirks and says they knew, but she persuaded them it was in their best interests not to tell.
- Fiore and her peers are surprised to learn Oda Nobunaga is a woman. As in canon, no real explanation is ever provided. Apparently she openly ruled as a woman and for some reason history recorded her as a man.
- The Ambition of Oda Nobuna involves a Sengoku Period universe where equal primogeniture was widely used. Because of this, many, but not all, of the big names of that era are female in this series, for example Oda Nobunaga (i.e. the titular Nobuna), Tokugawa Ieyasu, Akechi Mitsuhide, Date Masamune, etc.
- Boku to Tsundere to Heidegger depicts famous European philosophers as high-school girls.
- The Grace of Kings and its sequels are comprised of characters who are mostly counterparts of historical figures connected with the founding of China's Han dynasty, with the first book being about the Chu-Han Contention, and the second about the aftermath of Liu Bang, called Kuni Garu in the novel, gaining the throne. One of Kuni's allies is the street rat turned general Gin Mazoti, who is a gender-flipped version of Han Xin, whose backstory is essentially identical to that of the historical figure (or at least legends about him), except for an added element of Sweet Polly Oliver.
- Hyakka Ryouran Samurai Girls is a "Jidaigeki figures reincarnated in the modern world" example... but it's an Alternate Universe where modern Japan still looks like Jidaigeki.
- "Once and Future" by Terry Pratchett is about a time traveller called Mervin realising that he's at the beginning of the Arthurian era and in the perfect position to be Merlin. It ends with the youth who pulled the sword from the stone (an electromagnet controlled by Mervin) removing her hood, and Mervin frantically trying to remember if Nimue ever actually told him the sex of Uther's lost heir. (She didn't, probably on purpose.)
- Once and Future by Amy Rose Capetta and Cori McCarthy is a Space Opera in which refugee Ari Helix discovers she's the reincarnation of King Arthur, and Merlin is utterly bewildered because Arthur has never reincarnated as female before.
- In Ulysses: Jeanne d'Arc and the Alchemist Knights, Arthur de Richemont, Philip of Burgundy, La Hire and Charlotte de Valois are all gender flips of characters from The Hundred Years War. Considering it is from the same author as The Ambition of Oda Nobuna above, is no surprise.
- In the third series, Blackadder writes a novel under a female pseudonym and mentions that most of the famous "female" authors of the period, including Jane Austen and Dorothy Wordsworth, are doing the same: "James Boswell is the only real woman writing at the moment, and that's only because she wants to get inside Johnson's britches."
- The fourth series includes a sexual-orientation version: Oscar Wilde is mentioned as being a huge, bearded man, the father of hordes of illegitimate children and the author of a treatise called Why I Like To Do It With Girls. It was only down to an Amoral Attorney that he was convicted for homosexuality.
- Doctor Who: "Extremis" reveals that Pope Benedict IX was actually a woman, who the Doctor claims could do naughty things with castanets, in a clear reference to the legendary "Pope Joan". However, the episode is revealed to be almost entirely a computer simulation. But, as the simulation's creators tried to make it as realistic as possible, the claims about Benedict IX could still be true In-Universe.
- Drunk History has Alexander Hamilton and Aaron Burr being portrayed by females, with no attempt to hide it.
- In Legends of Tomorrow "Camelot/3000" has two of these. Stargirl having traveled back to Camelot is revealed to actually have become Merlin. In addition, while most of the Arthurian figures are present, there is a noticeable absence of Lancelot, that is until Guinevere says to Sara "I enjoyed meeting you, Sara Lance-a-lot", revealing Sara to be the inspiration for the legendary knight who wooed Arthur's wife.
- In the Red Dwarf episode "Parallel Universe" the protagonists come across a gender-flipped reality where the first person to walk on the moon was Nellie Armstrong, the most famous writer was Wilma Shakespeare (whose plays included Rachel the Third), and an influence on the "masculist" movement of the '60s (when they burned their jockstraps) was Jeremy Greer, who wrote The Male Eunuch.
- Warehouse 13 does this with H.G. Wells. Not only is the famous writer made female, but she is also a Mad Scientist who actually invented quite a few of the devices featured in the books, with her brother Charles acting as H.G. Wells in public.
- Fate Series:
- In Fate/stay night and Fate/Zero, the female Saber's (now very well known) true identity is a gender-flipped King Arthur, commonly known as Artoria Pendragon. It should be noted that she is quite insistent on being called "king," and spent most of her life doing everything she could to ignore or hide her female gender. Due to sexism, she didn't have much choice. A relatively small core of her inner circle knew the truth, including Merlin, Lancelot, Gawain, Guinevere, and her older foster brother Kay. Certainly puts a different spin on Lancelot and Guinevere's affair, doesn't it?
- In Fate/Apocrypha, Assassin of Black is gender-flipped Jack the Ripper (though justified as Jack's true identity is unknown, and while Assassin of Black killed prostitutes, she doesn't know for certain if she was Jack due to her vague memories) and Saber of Red is a gender-flipped Mordred (created through a bizarre set of circumstances involving sorcery who, like her "father," insists on not being treated as female). Non-historically, it also has a gender-flipped Frankenstein's Monster, because Victor Frankenstein always intended to make a pair (instead of being blackmailed by The Creature to make a mate) but just made "Eve" first and was turned off after seeing how she turned out with her wanting him to finish the job.
- Fate/strange fake changes genders without flipping the male/female binary. Enkidu gets changed from being male to having No Biological Sex and an androgynous appearance (depending on the translation, they're given "he" or "they" pronouns). There's also another iteration of Jack the Ripper, this one a personification of Jack's legend; they have no fixed gender, and are able to take the form of anyone or anything that's been identified as Jack, including Assassin of Black.
- Fate EXTRA features a gender-flipped version of Nero as the playable Saber. It also has a female Francis Drake as the Pirate Girl Rider, originally implied to be Queen Elizabeth in disguise, though later games have dropped that interpretation. Fate/Extella: The Umbral Star, the spin-off, added a female version of Attila the Hun (who was more notably an alien superweapon).
- Koha-Ace features a genderflipped Oda Nobunaga and Okita Souji. The rest of the cast retain their historical genders until the introduction of Nagao Kagetora. Since it's a gag series, it isn't treated particularly seriously, but Nobunaga has actually been fleshed out a bit more in later, more serious works, where she crushed all dissent through force and ruled openly as a woman.
- Fate/Grand Order, having a huge cast compared to most other entries in the franchise, has naturally added many more examples, such as Minamoto-no-Raikou and her descendant Ushiwakamaru. As early as the first event, the developers had already begun to parody the trope with Artemis, who originally pretends to be a gender-flipped Orion, and the cast buys it before the real Orion, whom she's trapped as a stuffed animal, starts to speak up. In fact, gender-flipping historical figures has gotten so common that the franchise has begun to try to be clever about it. Miyamoto Musashi is a woman, but she actually comes from an Alternate Timeline while the "main" Nasuverse's Miyamoto Musashi is explicitly referred to as male. Leonardo da Vinci appears as a woman, but is confirmed to have been male in life; his obsession with aesthetics and the Golden Rule (Beauty) skill altered his appearance and gender into that of the Mona Lisa (not that da Vinci seems to mind). And the original Katsushika Hokusai takes the form of a tiny octopus that floats near his daughter Oui (the "Servant Hokusai" is both of them, since Oui produced some of her own art under her father's name).
- The practice in Fate/Grand Order is Justified (and mocked) in the parody manga Learning with Manga! FGO, where the implied reason for the genderflips among the original Servants' ranks is due to the protagonist being a lesbian with a "no boys" policy. This is the origin of the Paul Bunyan servant in the game, who doesn't understand how on earth she became a small girl.
- Fate/Requiem: Erice Utsumi ponders on the series' tendency to have men in history and myth actually be women, using Francis Drake as an example, as all of her contemporaries remember her as either male or female. Erice concludes that Drake's actual gender doesn't really matter, compared to the great feats achieved. So far, the Greek mathematician Euclid has been revealed as a woman.
- In the Three Kingdoms Era of Inazuma Eleven GO 2: Chrono Stone, when the heroes finally meet Zhuge Liang she turns out to be a woman.
- Magoichi Saika is depicted in Sengoku Basara as a red haired woman. In this case, "Magoichi Saika" is the title worn by the current leader of the Saika faction. Magoichi is proud to announce that she's the first woman to carry the mantle.
- Toyosatomimi no Miko is a shikaisen version of Prince Shotoku. Why the history books record her as a man is unexplained, though it should be noted that Touhou has an Improbably Female Cast.
- Hieda no Akyuu is a milder example - she's the latest "Child of Miare", a line of Reincarnations of Hieda no Are, but the only memories of his that she retains are scholarly knowledge. Possibly inspired by theories that Are was actually a woman.
- KoihimeMusou is an all-female version of Romance of the Three Kingdoms. The only historical female-to-male flips in the franchise are Chousen and Himiko, both of which are extremely beefy deep-voiced men in microbikinis. That said, it's also an Alternate Universe and involves travel across time, space, and parallel realities.
- In the retelling of the story of Moses on Rugrats, Angelica plays the Pharaoh.
- The Simpsons occasionally does this, for instance, portraying Lisa as "Connie Appleseed" (Johnny Appleseed).
- Gravity Falls: In "Irrational Treasure", while investigating about the town's foundation, Dipper and Mabel find out about a few ancient national secrets, including that Benjamin Franklin was a woman.