Fics where a spell turns both of them into females are rare and I don’t think I’ve ever read them. You’ll find many fics where one of the two is genderswapped as result of a curse or a spell-gone-wrong.
Anyway, I’ve put together some fem!Arthur and fem!Merlin (most of them have canon-setting).
Merthuretta series by doctor_badass
Arthuretta has hidden things from her mother, Uthra, in the past, like her training to be a knight, but never as strange or unexpected as this. Merlina, her servant, has seemed to have affection only for her lover, Morgan, but she slips up one time, and everything is flipped. Genderwise, that is. ;)
The two of us are a perfect fit by kim47
Merlin looks at Arthur like she’s everything.
You & I by hopeisathreat [WIP]
Merlin and Arthur are both girls, met through the internet, have no clue with gender the other is but are hopeless for one another anyway. This is basically just Merlin being ridiculously excited over Arthur soon coming over.
Sealed with a kiss by luu1234
Princess Arthur of Camelot hates having to act like, well, a princess. She’s always felt for comfortable in armor than in dresses. One day, as a result of an argument between Uther, Arthur stormed out of the castle and takes a walk in the forest, where she finds Merlin. A girl who seems too fond of the idea of execution, talks to animals and is apparently a socerress.
Five Necessary Fact by Sham
The first thing you need to know about Princess Arthur is that, no, it is not her name.
Carry You Up by ur_lionheart
The one where Merlin is hit by an arrow, Arthur carries him up a hill, and there’s an almost kiss.
Lies by tibbins
Melin is hurting. Arthur wants to help but Merlin won’t let him in. What could possibly scare Merlin so? And why is he desperate to get out of Camelot?
Somebody To Lean On by samyazaz
Merlin may be the worst manservant ever, but when he breaks his arm and Arthur has to care for him, he quickly discovers that he’s kind of terrible at it, too.
Strip your sleeves and show your scars by manetsolus
Merlin does not usually undress completely before Arthur, bathe with him, linger after sex, nothing. Arthur craves nothing more than to touch Merlin and explore every inch of his skin but Merlin doesn’t let him. At least, not until one night, when he lets Arthur strip him and falls asleep without fuss after they make love and Arthur counts it both as a blessing and as a curse. It shouldn’t hurt to get the things you want.
The Way We Love by wobaozhewo
Merlin gets hurt, but makes it out to be no big deal so Arthur won’t worry. Then comes the pubs.
We have two lists (one & two) on our delicious page that meet this criteria, and also another one that has both sick!Merlin and sick!Arthur.
Otherwise, here’s some more for you, anon. They range between true slash and bromance/pre-slash:
All Your Perfect Imperfections by ariadne_odair
"I can’t stay here, I’ve got school," Arthur says, patting his head, and Merlin pouts, grabbing his wrist. "Pleeaseee, Arthur. Stay." Obviously, ill Merlin isn’t rational Merlin. Arthur kind of wants to punch himself about how cute Merlin is.
Not a Jest by Emiliana Kiladry
Merlin has developed a cough and falls ill. When he and Arthur are kidnapped, the prince is hurt and imprisoned while Merlin is fading. A little magic might not even be able to save them.
You’re Not Allowed to be Ill by Merthur
When Merlin gets a cold Arthur worries a bit too much.
Your Idiot by bravenclawesome
Arthur fell to his knees and buried his face in Merlin’s shoulder, trying to hold his emotions in, but the tears were already running down his face in careless abandon. “Never – do that – to me – again,” he choked. “I could have killed myself when I saw you - I thought you were dead. How could you have been so stupid?”
In My Defense, Spring by schweet_heart
Arthur comes back too early, because he can’t stand watching Merlin suffer alone.He always did have terrible timing. (WARNING: READ TAGS!)
Paint the Skies Blue by cat_77
Merlin is a painter with a secret. Arthur would prefer if that secret didn’t kill him.
Don’t Overdo It by bevinkathryn
“You’re such a baby,” Arthur taunted without any heat, smoothing Merlin’s hair off of his forehead. “I had the exact same cold and I wasn’t nearly this bad.”
Merlin Falls Ill by Anon
Arthur accidentally shows his loves for his servant after Merlin falls ill in his chambers.
Who’d have thought? by underratedsnail
In Merlin’s eyes, they were enemies. Gwen thought he was being stupid. Merlin didn’t care; he’s hated Arthur since he first came here, why would that ever change?
When We Bleed We Bleed The Same by hms_seth
It all would’ve been simple enough if Merlin had just hidden his magic for a few more months, and not…very publicly used it to save Arthur Pendragon’s life. As it stands, things are definitely changing.
A lever and a place to stand by twoskeletons
When a peaceful march for the equal rights of magicians ends badly, Merlin is forced to hide out in the apartment of law student Arthur Pendragon.
Just a stalkerish alien perverted prat by underratedsnail
Arthur is an alien prat and Merlin has a lot of confused feelings.
Cellmate by lcacbc
Merlin is dead. No, really. He has just called the most powerful man in prison a prat. A prat he just happens to be cellmates with.
Patience and Persistence by digthewriter
Merlin just wanted to prove his worth in academia and his importance on the rugby team. He didn’t mean to start shagging the only bloke he couldn’t stand. He also didn’t understand what was so great about him—why did everyone love Arthur so much?
Pendragon’s Darling series by Deminos
In an attempt to pay back his father’s debt, Merlin Emrys agrees to trade to Mafia Boss a very precious commodity: his virginity. Little did he know that Arthur Pendragon also had a certain kink for stockings, garter belts and bondage…
Red Knight and Magic Man by thecheekydragon
A.J. Pendragon tries to sort out his feelings for Merlin. Sometimes he couldn’t stand the guy, but there were other times…
I don’t know if being a spy or an actor is considered something equally important to a prince or politician, but I put a couple of those as well XD
The Booth in the Corner by ambrosius
When Merlin befriends the lonely man he always sees in the morning at his local coffee shop, the last thing he expects to happen is to fall for him. Let alone find out the man is actually Arthur Pendragon, the Prince of Wales.
Just Have To Save The World (Back In A Minute) by ZairaA
In which Merlin is convinced that Arthur is the worst flat mate ever and also an - unfortunately gorgeous but promiscuous - accountant. Until he’s abducted by weird Russian guys with guns; then he starts having his doubts.
License to Thrill by lady_ragnell
Merlin’s employees bet him the recipe for the most addictive cocoa in the world that he can’t find out what the hot blond who comes into his chocolate shop does for a living within the month. He ends up getting far more than he bargained for.
We’ll Be a Dream by Sarageek16
Arthur and Merlin literally collide when they are five years old. From there, they slowly, stumblingly grow into their connected destinies as the king and his wizard.
Fan Favorite by harrycrewe
Written for this prompt: Where one is a famous celebrity of some sort (movie star, musician, royalty, etc) and the other is a shamelessly enthusiastic fanboy who during a celebrity-meet-and-greet/convention panel/concert/whatever asks the other to marry him/go out on date and of course, the other much to everyone’s surprise and especially the fanboy’s says yes.
Now That I’m Rich They Give Me Coffee by lady_ragnell
Arthur’s a rock star, Merlin doesn’t live under a rock, Morgana’s badass, and Will is the worst best friend ever.
Same River Twice by kianspo
When Arthur, the Prince of Wales, was seventeen, he made a mistake that is still haunting him. Eight years later, can he finally make it right?
Drastically Redefining Protocol by rageprufrock
In which Prince Arthur meets Merlin and all hell promptly breaks lose.
The Meat Feast by cornmouse
Merlin is a BNF fanartist for The Roman, a camp HBO gladiator show. He accidentally becomes involved with The Roman’s lead actor, Arthur Pendragon, over Skype without realizing it. Many pornographic shenanigans and misunderstandings ensue.
Here you go:
Heartstrings by hulubululu
Merlin is oblivious and Arthur has to resort to music to get his message through.
Destinies Are Troublesome Things by AnalystProductions
In which Gwen resorts to Facebook stalking, Merlin plays matchmaker, and a confident stranger called Arthur - ‘future boyfriend’ according to his t-shirt -serenades Merlin glee style in the middle of the shopping centre. Since when did this kind of thing actually happen in real life?
Karaoke Night! by ella_bane
Merlin loses a bet, but turns the tables on Arthur.
One Song by Trojie
They’re paired by their music teacher for their final assessment, a Battle of the Bands-style playoff. Unfortunately, she doesn’t know that a bit of high school drama went down at term-break. She doesn’t know what this one song she’s making them play might mean to both of them.
Surprise Karaoke by elirwen
“Now, silence please.”
She waits for the crowd to calm down.
"Enjoy the show,” she says and leaves the stage, taking the microphone with her.
Greek God by cumberass
For the KMM prompt: Today, I peeked through my window and trained a pair of binoculars on my neighbour’s house. Every night without fail, he ends up standing in front of his window topless to flex his muscles. This time, I was surprised to instead find a note taped to the window saying, “Sorry, I’m out tonight.” FML.
With Stars In Their Eyes by alba17
In which Merlin plays the guitar, Arthur wears eyeliner, and everybody wants to get famous by winning You’re The Voice.
Here’s a few :)
Knights should never play with dragons by thecheekydragon
Merlin hated Arthur Pendragon. He really, really did. Now he was going to have to spend three weeks as a camp leader at a summer youth camp with him?
Just another camping story by miss-chevalier
Merlin’s class goes on a camping trip and of course Merlin’s secret crush Arthur Pendragon is going, too.
Magical by obstreperouscharacters
Merlin and Arthur are the two fastest runners on the Camelot High School cross country team, and the fact that they hate each other is not exactly helping the team’s work ethic. So, when the group takes its annual trip to an out of state meet, Leon, their coach, decides that Merlin and Arthur are going to become friends. The rest of the team is hoping they’ll become a little more than that.
Come Around by andiwould
When Merlin finds himself rooming with Arthur on a high school field trip and the cold forces them to share a bed for warmth, the last thing he’s expecting is to end up hooking up with his prattish classmate.
Amid the Pines that Stood by Emjayelle
On their day off from working at Camelot Camping, Merlin and Arthur escape to the other side of the lake for some much needed alone time.
The Scout who came to Camelot by maidentashincamelot
Merlin, Will and Mordred are Senior Scouts who go to their club in Ealdor. But when their scout group closes up due to a lack of members, their former leader Tom transfers them to the Camelot division, already having his son Elyan in the group. Tom also transfers his daughter Gwen and her friend Elena to the Camelot Girl Guides, as their pack have also discontinued. Joining the Camelot group, he is placed under the supervision of Arthur Pendragon, who ‘supposedly’ tries to make him feel at home. One accident to Merlin, and Arthur’s feelings change for the lad though.
Love Spells, Tarts and Other Food-Related Endearments by Mamalaz
Arthur on a love potion was always a nightmare but Arthur on a love potion that actually bewitched him to be in love with Merlin was about a hundred times worse to deal with. Mainly because it really wasn’t a hardship for Merlin at all.
Darling by Violette_Royale
Darling, Arthur calls him.
Breathless by tracy7307
When Merlin is ill and has an asthma attack, Arthur helps him to breathe again.
Slip by Thursday_Next
This is the point where Merlin’s supposed to say ‘how do you like my Halloween costume’ or ‘hey, I got that part in that play’. But he doesn’t. He doesn’t, and the implications of that wash over Arthur like a wave of heat.
Baby Boy by solostsobroken
Arthur has called Merlin his “baby boy” ever since they were toddlers. Merlin never really questioned it. It was simply the way things were. But when a new kid named Gwaine arrives and stirs things up, Merlin finally learns that the name has a deeper meaning than he originally thought…
Love is an expression by helloearthlings
Arthur’s brow wrinkled as he gave Merlin a look that wouldn’t have been out of place back in Camelot after Merlin called him a clotpole, or a dollophead, and fuck, Merlin had just called him love, hadn’t he?
And For You I Bloom by Deminos
Merlin is a doctor-in-training serving under Gaius. He’s content with his life, never thinking that he would cross paths with anything remotely close to romantic love. That is, until he meets Lord Arthur Pendragon. Then the longing and sheer attraction that Merlin feels begins to fester within his chest like a persistent weed and he’s sure that Arthur feels the same way, even if he doesn’t show it. They fall in love, one flower at a time.
Little Falcon series by surrenderdammit
Series of related stories about the romantic relationship between Always-a-girl!Merlin and Arthur. It’s completely AU and plotless; mostly porn and fluff. Set in Camelot.
I stepped out of time and landed in your lap by surrenderdammit
Suddenly he remembers how young Merlin looked in their bed, how he trembled and how he blushes. How he’s dressed in those old rags of his servant days that he hasn’t seen in bloody years. Groaning, Arthur ends the kiss and leans his forehead against Merlin’s. “Please don’t tell me I’ve been sent back in time and took you to bed like a brute.”
Stay With Me by BeneaththeHalo
When a coughing illness takes hold of the lower town as well as the castle’s servants, it isn’t long before it also claims the king. Of course, it falls on Merlin to look after Arthur while he’s sick, and while he is prepared for all manner of protests about remaining in bed, he ISN’T prepared for what Arthur asks him to do.
Endorphins by sadtomato
Sick Arthur is, of course, whiny and demanding. Merlin takes care of him.
Feverish and Bedridden by Lunadeath02
Arthur is very ill and he will only let Merlin treat him, but the medicine he took makes him hallucinate, and the truth comes spilling out.
Give Me Fever by La_Temperanza
So when Arthur caught a cold, instead of being sympathetic, Merlin just pointed and laughed, blaming Arthur’s poor life choices up to that point in time. And when Arthur coughed into a tissue that would probably need a hazmat team to properly dispose of, moaning under a plethora of blankets, “Stop laughing Merlin, this is serious. I’m probably dying,” Merlin just laughed even harder. With more exaggerated pointing as the cherry on top of his “I told you this would happen, you slob” sundae.
Patience by myashke
When it comes to caring for his stubborn prince, Merlin has to get creative.
The Red Rose by rotrude
War of the Roses AU. The year is 1461 and strife is ripe between supporters of the houses of Lancaster and York, King Henry VI’s Queen and Richard of York’s sons, supported by the Earl of Warwick. The second Battle of St Albans pits one camp against the other. One knight seemingly falls, forgotten by everyone except the man he’s rescued by, Merlin, who tends him when it seems he has no future.
Let Me Take Care of You by bleedforyou1
Arthur is so ill, he can’t even bring himself to eat, so Merlin has to feed him.
Delirium by mithrel
Arthur has a fever. While he’s delirious, he gives something away.
What Ails You by adelagia
In which Arthur is sick, whinges a lot, shanghais Merlin into a serious conversation, and talks of forever.
Something Borrowed by EachPeachPearPlum
When Merlin proposes to his sister, Arthur knows nothing will ever be the same between them, and he can live with that. He won’t be happy about it, but even if he’s loved Merlin for years, he’s not going to stand up at their wedding shouting, “I object,” not when it won’t do him any good.
And then the stag night happens.
The Dreams Inside by winterstorrm
Arthur had always held back, not trusting himself. After all, he’d been in love with Merlin since he was eighteen years old—and Merlin had been with his sister. Now that Morgana was off the scene, could Arthur be blamed for taking his chance with Merlin?
Dedication by lady_ragnell
In which Merlin and Morgana have a lot of sex, but Merlin falls in love with Arthur anyway.
FML by thecheekydragon
Popular girl Morgana Pendragon wants Merlin. Apparently, her brother Arthur does also.
Arthur in Real Life by wickedtrickstah
When widower Arthur Pendragon meets a man named Merlin at an Outdoor Store during the annual “Labor Day Pendragon Family Reunion Weekend”, it’s love and ‘sexual-identity-crisis’ at first sight. The problem is, his sister Morgana found Merlin first.
Merlin and Morgana are not actually dating in these two, but Arthur thinks they are:
Pieces of Us by dentedsky
Morgana is pregnant and doesn’t know who the father is, Gwen sleeps around with all the wrong men, Merlin meets Arthur and thinks he’s a tool, Arthur is getting married to the wrong person (who knew!) and it is possible Arthur is, actually, a complete tool after all. Or: Wherein Morgana Hires Merlin to Pretend to be Her Boyfriend So Arthur Doesn’t Find Out She’s a Big, Big Slutty Person.
Always the Last Place You Look by thalialunacy
Sometimes, destiny is all about bad timing.
When Merlin woke up this morning, he expected to go on about his life as a 20-something curse-blocked (don’t ask) barista with a cat named Eomer (don’t judge) and a tendency to get distracted by his own imagination. He certainly didn’t expect to end the day engaged to the woman of his dreams.
Probably because he’s never spoken to her. She also happens to be unconscious.
But she’s suddenly his and Merlin finds himself stumbling over exes, ethics, and the fact that she comes as part of a package deal, along with an overbearing father, a group of friends-in-law that should have their own sitcom… and a brother named Arthur, who takes all of Merlin’s assumptions about his life and turns them onto their heads.
Sometimes, destiny is also about misdirection.
All The Complexities by coeur_de_ma_vie
The course of true love never did run smooth. Arthur and Merlin knows this all too well.
Euphoria by Nyxelestia
Even with his veins flooded with heroin and suppressing his power, and even when he rides high on the chemical bliss, Merlin’s magic still sings for Arthur. And Arthur has answered the call.
The Milk of Paradise by fitz_y (historical)
San Francisco, 1869: The gold rush is over, the opium dens are booming.
Time’s Up by Detochkina
Is there anything in common between drugs and excellent grades? Or business and psychology? The answer is simple – in the world of big money a lot can happen when you’re bored to tears. Under pressure from his father, Merlin becomes involved in a strange relationship. At first, he can’t get out of it; on second thought – he doesn’t want to.
Can’t live with you. Can’t live without you by weepingelm
Arthur is always working late then one evening he gets back to the flat to find it empty and a note from his partner.
Junky by opheliac_fairy [WIP]
Arthur is a CEO. Merlin is a drug dealer. The two mix better than you’d think.
The Lost Boy by kurohitenshi
Just because someone is homeless and unable to escape drug addiction does not mean that his life was any less important than yours or mine. Maybe there are circumstances. Maybe there are reasons. Cathal O’Regan is determined to leave a legacy behind through a short memoir in a small leather-bound book, along with the hint of the greatest secret of all: something that this life could not fulfill.
Also check the addiction tag for more various lists with similar themes ;)