Royalty AU

A Royalty AU is a fanwork set in an alternate universe where one or more characters (who canonically aren't) are members of a royal family. This usually goes hand in hand with a historical period, featuring a Medieval AU or Regency AU, although some works are set in Modern times or even the Future. Fusions and pastiche/crossover with fandoms that have canon royalty are quite common. The genre is popular, with approximately 13000 works on AO3 (December 2020)
The Modern Royal Family AU trope is very common in Merlin fandom; in it Arthur Pendragon and members of his family are still royals, but transported into a modern setting (usually taking the place of the current British royal family).
These AUs are generally distinct from RPF fanfic about real present-day royalty, Royalty RPF.
==Example Fanworks==
The 100:
* To Kill A King by nighimpossible, a Bellarke fic where Bellamy is an lowborn orphan daring to dream bigger than his meager beginnings, and Clarke Griffin is a princess engaged to be married to the prince of the Jaha Kingdom. In a land where corruption and greed rule both the castle and the city streets, both Bellamy and Clarke will learn the true cost of what it takes to kill a king. (Medieval AU)
* What heart's ease must queens neglect by thrace, a Clexa fic where Lexa is the Queen of a fictional country in the middle of democratization, and Clarke is a United Nations election observer sent to oversee the process. (Modern AU)
The Avengers (Marvel Movies):
* A Storm over Xela by Cakeisnotpie, a space drama where Heir apparent Phil Coulson, switch places with cousin Jasper Sitwell to enjoy his last days before marriage to Melinda May, Initiate Prime. Steve Rogers, Captain of the Guard, just wants no one to get hurt under his watch. And Clint Barton, spy and security expert, just wants to be wrong about his suspicions. None of them are going to get what they want ... but they might get what they need.
* I don’t wanna let you love somebody else but me by TardisIsTheOnlyWayToTravel, A Darcy/Natasha Princess/Bodyguard AU. (Story has been deleted - link via webarchive.org)
* Stars hide your fires by boleyn13, a Loki/Tony Stark fic in modern setting with Loki as the second prince of a fictional state (2017-2020)
Bandom
* King and Country by tabulaxrasa - a Historical AU where Gerard Way is King of the semi-fictional country of Illyria. Gerard/Frank.
Boku No Hero Academia
* Wonderful King, an Iideku fancomic featuring prince!Deku and knight!Iida. 
Generation Kill:
* Kings and Vagabonds by noelia_g - fusion with The Princess Diaries;Teenage Brad Colbert turns out to be heir to the throne of a small European kingdom.
Hanson:
* Watch The Throne by Selina, which casts the brothers as princes of a fictional micro-country.
Harry Potter:
* Avalon in Arms by potterlad81, in which Harry is King of Avalon, a technologically-advanced magical country.
IT:
* Untitled F6 + A3 by eddiefuckinkaspbrak, in which Eddie Kaspbrak and Richie Tozier are princes of neighboring kingdoms.
Dream SMP/MCYT
* Passerine by Blujamas - royalty and Fantasy AU fic drawing on medieval and renaissance vibes, primarily featuring Tommyinnit, Philza, Technoblade, Wilbur Soot, and Kristen (aka SBI) as a ruling family of a smallish kingdom with Philza as main ruler. Including Angst, drama, and diplomacy. 
Merlin:
* The Crown of the Summer Court by astolat - canon-setting fic in which Merlin is a fairy prince.
One Direction
* See It Turning Red by dinosaursmate, is a canon divergent fic where Harry Styles is a prince who employs escort Louis Tomlinson to a function to spite his father.
Teen Wolf:
* The Well of Living Waters by Kalpurna - An arranged marriage fic, set in Medieval AU - King Derek takes a consort in the form of Stiles.
* The Hollow Prince by Runningwithwerewolves - Inspired by a Grimm Fairy Tale about a big bad wolf & a young girl in a red hoodie, an angst with a happy ending Medieval AU tale of Royal Hales with magic, mystery, and romance.
* Waiting Games by Jerakeen - Stiles is the only Heir to the throne, featuring marriage of convenience, in an A/B/O AU.
* The Exchange by GoddessofBirth - Prince Chris Argent sends to the Hales to fulfil an ancient marriage treaty, not expecting Peter Hale to arrive at his doorstep. arrange marriage trope.
* Like Heaven Catching Lighting by weathervaanes - Prince Stiles of Cor has always known, somewhere in the back of his mind, that he was never truly going to marry for love. Fighting it has only made it worse. Now, presented with a choice between two children of the Hale family of Ignis, Derek and Cora, he must make the decision to determine who will rule by his side. If only it were that simple.
* A Desperate Arrangement by mikkimouse - After seven years of lengthy negotiations, the treaty between the Hales and the Argents has fallen apart and the two countries fell into war. Months later, there's an uneasy truce, thanks to the intervention of King Scott McCall, but it won't last. In a desperate attempt to maintain the peace, the Hales sign a treaty with the McCalls to marry Prince Derek to Prince Stiles Stilinski, King Scott's brother. In the history of the world, there have been many better ideas.
Star Trek:
* strive seek find yield by waldorph - fusion with The Young Victoria; Spock is heir to the Federation throne and Kirk is a rebellious princeling.
Stargate Atlantis:
* Fair by Minnow - canon-setting fic in which John is a fairy prince.
* The Spare by Rachael Sabotini - Elizabeth Weir is Empress of a fantasy steampunkish empire and John the royal family member who must make a marriage of convenience with Rodney.
* Evil Overlord Sheppard by GraceandFire - John is Imperial High Ruler of the planet Leiath.
Stray Kids:
* - Han Jisung by TokimekiBunny, published 10 November 2023
Supernatural: 
* Prince Castiel and the Quest for 100 Orgasms by Luchia - Crack Fic in which Castiel knows gladiators can win their freedom by winning 100 fights, so Castiel has decided to operate under the assumption that if King Dean has 100 orgasms, he might let Castiel go.
* The Dreamer and the Mystic by Bellanovaskies - a Dean/Cas Big Bang 2012 Fic where Dean was expected to choose his Queen-To-Be at his 18th birthday; instead he found himself falling for a mysterious stranger with eyes like stars. Eleven years later, accompanied by his brother and their father’s knights, Dean journeys into ancient lands that have long since faded into legend and lore, to once again find the eyes that had bewitched him. Castiel's tribe may be a force to be reckoned with, but nothing can prepare Dean to face his own father, and confess his love for a less-than-human being.
Supernatural RPF: 
* Our Story Is Infinite by elizah-jane - college AU in which Jensen is a fairy prince.
==Archives & Fannish Links==
* Alternative Universe - Royalty works on Ao3
* Recs tagged Royalty AUs at Fancake
==References==