- "Every fairytale needs a good old-fashioned villain. You need me, or you're nothing."
- ―Moriarty to Sherlock [src]
James "Jim" Moriarty was the world's only "consulting criminal"; a stark contrast to his arch nemesis is Sherlock Holmes' similarly unrivaled "consulting detective" occupation.
In 1989, when he was 13 years old, Moriarty murdered Carl Powers, whom he claimed "laughed at him". He kept Powers' trainers almost twenty years until he used the shoes as part of his plan to meet Sherlock Holmes and had them planted in the disused flat at 221C Baker Street. 
From that point onwards he developed and trained his skills at criminal activities and went on to create a large criminal organisation which would stretch across the whole globe.
Operating behind the scenes
Moriarty acted as a sponsor, an informant and a mastermind. He is shown to have an interest in sherlock that borders on obsession, though he does not hesitate to try to kill him when he loses interest. In his operations, there is never any direct contact between Moriarty and his clients.
Jeff Hope, one of Moriarty's clients, attempts to murder Sherlock, but is shot dead by Dr John Watson, Sherlock's friend and flatmate. Hope had previously revealed that he had a sponsor, but refused to tell Sherlock his name. Only when Sherlock stamps on Hope's bullet wound does he eventually scream, "MORIARTY!" 
Later, Moriarty assists in smuggling the Black Lotus criminal organization into Britain. Sherlock and John thwart their plans, though. The leader of the organization, General Shan, has a brief conversation with Moriarty over her laptop, and is shot by one of his snipers so that she cannot reveal his identity. 
Moriarty eventually decides to play a "game" with Sherlock, forcing him to solve mysteries within a time limit and taking hostages to ensure that Sherlock is properly motivated. He also disguises himself as Molly Hooper's boyfriend Jim and visits Sherlock in his lab when he is trying to solve a mystery. Sherlock, unaware he is Moriarty, "deduces" that he is gay (though this was a plot by Moriarty), which upsets Molly.
Revealing himself to Sherlock
When Sherlock has solved every mystery, he finally meets Moriarty at a swimming pool. Moriarty has taken John hostage and wired plastic explosives to him, while having a sniper aimed at him. In an intense showdown, Moriarty warns Sherlock to back off, saying he will "burn the heart out of [him]" if he does not. Moriarty then leaves, and Sherlock rips the explosives off John and tosses them away. However, Moriarty then reappears along with dozens of snipers, saying they cannot be allowed to continue. Sherlock aims at the explosives he took off John, intending to detonate them and take Moriarty with him. 
Moriarty's phone rings, interrupting them. After a few words with the caller, Moriarty leaves for good and calls off the snipers.
The caller is revealed to be Irene Adler. Moriarty constantly gives her advice on how to manipulate the "The Holmes Boys", having given them both nicknames. It is also mentioned that he asked for nothing in return, becoming involved just to cause trouble, suggesting his obsessions are deepening. 
Bringing down Sherlock
It is also alluded to that he might have an independent rivalry with Mycroft. At some point, he was captured and interrogated by Mycroft, but was released, the information he gave coming at a personal price to Mycroft. As he is leaving, it is shown he has repeatedly scratched the name Sherlock into the concrete walls of his dungeon, as well as in reverse on the two way mirror. 
Shortly after this, Mycroft called for Moriarty to come to the Sherrinford maximum security prison in order to meet he and Sherlock's secret sister Eurus Holmes, who requested to spend 5 minutes alone with Moriarty unsupervised as part of a Christmas present.
Later, Moriarty is seen outside Tower of London dressed as an ordinary civilian, and after walking into the room where the Crown Jewels are kept, he then puts on his earphones and begins listening to Rossini's "A Thieving Magpie." Taking out his Droid Incredible S, Moriarty presses a button bearing the emblem of the Crown of England. From there, it is shown that the Bank of England, Pentonville Prison, and the Tower of London's security systems have all been breached at the same time. As London's police force, including Lestrade and Sally Donovan, drive hastily to the scenes, the alarm in the room begins to activate, and as the nearby guards tell everyone to leave, the whole of the room is emptied of visitors and guards. As the door closes, a guard asks Moriarty to leave but before he can speak, Moriarty sprays a canister of sleeping gas at him. Smashing the glass case around the Crown Jewels, he dressed in them and waited for the police to take him into custody, being found not guilty after the jury are extorted by him. Moriarty paid Sherlock a visit after to plant a false clue in his mind and assured him nothing was over yet, before leaving.
Later, Sherlock and John investigate the disappearance of two children of a U.S. ambassador from a private school in London. It is revealed that the day the kids disappeared was the same day the school term ended. So, with numerous parents and children surrounding the school, it was incredibly easy for Moriarty's man to blend in with the crowd, become unnoticeable and enter the school. Waiting until nightfall, the kidnapper walked towards the room where the children slept, armed with a gun. As a result of spending the majority of his school life in private education, the boy had become acquainted with all the shadows of all the people who passed the door, leaving a clue behind for the police. After grabbing hold of the two children, Moriarty's man held them at gunpoint and led them out of the school. From there, he transported them to an abandoned warehouse in Addlestone. The kidnapper then locked the terrified children in a cage in a cold, dark room. The cage was filled with hundreds of sweets. The wrappers of the sweets were lined with a deadly poison (mercury) that was gradually killing the children.
Moriarty had traumatized the girl, so upon meeting Sherlock, she would scream and become terrified of him, which was meant to convince DI Lestrade that Sherlock was actually potential kidnapper. Lestrade was then ordered by his superior to arrest Sherlock for kidnapping and John for punching Lestrade's superior in the face. After escaping from the police, Sherlock and John were now fugitives. After Sherlock and John break into the house of a journalist, they discover Moriarty. Seemingly terrified and shaking with fear, he tells Sherlock and John to keep away from him and begs John not to hurt him.
Reporter Kitty Reilly states that there never has been a man named James Moriarty and accuses Sherlock of inventing him, as well as all his crimes as a way of becoming popular with the media and building up a reputation of himself as a Private Detective. John refused to believe this, arguing that Moriarty had only recently been on trial for attempted burglary, and that Moriarty intended to detonate explosives to kill Sherlock and himself. Reilly countered by saying that Moriarty was actually an actor named Richard Brook that Sherlock paid to act as a master villain. Still in denial, John asks to be shown proof, from there the journalist shows him numerous papers about Richard Brook including various headshots and an actor's profile. Moriarty then claims to be playing the role of a storyteller to young children on television. Sherlock then shouts at Moriarty, demanding him to stop this lie. Advancing on him, Sherlock and John chase Moriarty as he escapes through a nearby window.
Later, at St. Bartholomew's Hospital, Sherlock texts Moriarty, who meets him on the roof. Sherlock claims that, with the code, he can completely delete all evidence of Richard Brook from the world. Moriarty says that there is no code, and the tapping rhythm that he did at Sherlock's flat was actually the beats to Bach's Partita No. 1. Moriarty said to Sherlock that his weakness was that he always wants everything to be intelligent and complex, so then he can solve it and brag about his intellect to others.
Moriarty explains that for the past 24 hours, he has convinced the general public that Sherlock Holmes is a fraud and a liar, therefore making Sherlock's once-great reputation completely shattered, and the only person who still trusted him was John. When asked by Sherlock how he managed to break into the prison, the bank, and the Tower, Moriarty replied that he simply bribed security guards to collaborate with him in his scheme. Moriarty's final plan was to drive Sherlock to the point where he would commit suicide to escape his shattered life, but as Sherlock had no wish to do so, Moriarty explained that he'd hired three assassins, strategically located around London, each one ready to shoot Sherlock's only three true friends; Lestrade, Mrs. Hudson and John. One was disguised as a police officer outside DI Lestrade's office, another was disguised as a repairman inside the Baker Street flat, and the final one was located in a tower building opposite St. Bart's hospital.
Moriarty is then revealed to know a word that only he could say, that when spoken, would call off the assassins. Sherlock and Moriarty then spoke to each other, and Sherlock coldly stated that, although Mycroft would just lock up Moriarty, he would most likely kill him, and that even though Sherlock seemed to be a kind person and "on the side of the Angels", Moriarty should never assume that he is one of them. Sherlock says that he is willing to do anything to activate the fail-safe. After acknowledging that he and Sherlock are alike (in the sense that Sherlock has a dark side), Moriarty realizes that as long as he is alive, Sherlock can activate the fail-safe and save his friends, so he produces a handgun from his coat pocket and shoots himself in the mouth. 
Two years after Sherlock's 'death', it was concluded by police that the actor Richard Brook was in fact an alias created by Moriarty and that Sherlock was innocent of fabricating Moriarty. Moriarty appears in numerous flashbacks and imaginary sequences when contemplating how Sherlock possibly faked his death.
Moriarty was also in Sherlock's mind palace, in solitary confinement and wearing a straitjacket. He taunted Sherlock but when John was mentioned, it gave Sherlock the strength he needed to recover from a serious bullet wound when he was near death. Moriarty's face was later broadcast all over England and spoke the words "Did you miss me?", forcing Sherlock to return from his exile early to work on the case.
On the flight back, Sherlock enters his mind palace in a drug induced state to unravel the unsolved mystery of Emelia Ricoletti, a late 19th century woman who, like Moriarty, shot herself in the head then appeared to rise from the grave. Afterwards, Sherlock concludes that Moriarty is still dead but it becomes a matter of explaining how he's manipulating events beyond the grave, with Sherlock telling John and Mary Watson that he knows what Moriarty will do next.
When Eurus Holmes traps Sherlock, John and Mycroft at Sherrinford, she plays pre-recordings that Moriarty made years prior in order to stress out Sherlock, with one of them being Moriarty going "tick-tick-tick-tick" when Sherlock is forced to work out one of her games.
- Sherlock: "People have died."
- Moriarty: "That's what people DO!"
- ―Holmes and Moriarty[src]
A criminal genius, Jim Moriarty was a sadistic and psychopathic individual. He exhibited the following traits: extreme intelligence, grandiosity, incapacity for remorse, arrogance, and an unhealthy degree of self-confidence. He also displayed highly Machiavellian traits. Much like Sherlock, he had a sarcastic, cynical, albeit childish sense of humour but unlike Sherlock he often spoke in a tone that would intimidate or annoy his opponents.
Moriarty was arranging the deaths of others from a young age. In 1989, he killed schoolboy Carl Powers. He appeared to be a highly efficient criminal businessman and had a humongous network of people at his command. Moriarty seemed to show, at least superficially, concern for children, as he paid Jeff Hope large amounts of money for his children every time he killed, however he actually has no care for them as shown when he had a bomb strapped to a very young boy.
Moriarty was obsessed with Sherlock Holmes and appeared to enjoy his role as a villain. Moriarty, like Sherlock, was willing to do anything to stop himself from getting bored. He was capable of frightening mood swings. He was ruthless, and committed torture and murder in sadistic ways, and when Sherlock accused him being responsible for people's deaths, Moriarty screamed at him 'That's what people do!', indicating that he didn't care if people lived or died. He also rather glibly referenced people's deaths when he was personally responsible, citing that Carl Powers 'laughed at me, so I stopped him laughing'.
Moriarty was a man who would resort constantly to humour regardless of the situation, especially when mocking people for falling for his deceptions - when he faced off against Sherlock at the swimming pool, he taunted Sherlock with the fact that he managed to convince the detective he was gay. When he played a sadistic trick on Sherlock with a derisive video during a taxi journey, he remarked 'No charge' when Sherlock discovered him. When Sherlock held him over a rooftop and threatened to let him fall to his death and labelled him insane, Moriarty shot back 'You're just getting that now', to belittle Sherlock.
Moriarty believed his only weakness (or at least openly suggested it to be) that he was extremely changeable - this was prominently shown in him first deciding to abandon his showdown with Sherlock, only to abruptly return and threaten Sherlock again.
It is very debatable as to whether or not Jim fears death - he showed absolutely no concern or fear when he was held at the point of a gun by Sherlock (most likely because he knew he had too many advantages on the man at the time), only to cry out when Sherlock threatened to throw him from a rooftop.
Moriarty is of average height, standing a couple of inches below Sherlock, and of a slender build, with dark black hair and pale skin. He can nearly always be seen wearing full dress suits (Westwood, to be precise), such as a dark blue one he wore in his first meeting with Sherlock and a grey one during his visit to the latter's apartment, often accompanied by a tie. As "Richard Brook", he seemed to put on a more standard image, with unruly hair and casual clothing.
- Genius-Level Intellect: Moriarty is incredibly smart. He is one of the most intelligent individuals on the planet, rivaled only by Sherlock, Mycroft, Charles Augustus Magnussen, and Eurus Holmes. His genius was strong enough that Moriarty was able to safely interact with Eurus in Sherrinford.
- Master Tactician: He was also clearly quite calculating and resourceful for his age, managing to retrieve an almost undetectable poison that would work effectively in the circumstances that Moriarty required. As a consulting criminal, he was able to consult his clients to do a wide range of crimes, such as murder, forgery, and theft of top-secret information.
- Master Manipulator: He was highly skilled at manipulation, and even Sherlock found it hard to predict Moriarty's next move. Also, he had complete mastery of terrorist techniques and intimidation strategies and knew exactly what buttons to press to pressure or enrage people.
- Expert Intimidator: He had an incredible capability for changing his tone of voice and behavior several times in a single sentence for psychological warfare - ranging from serenity, humor, mockery, childish, laid-back, to violence, and this will make the victim more terrified of him. Moreover, because of this, Moriarty is extremely difficult to read and anticipate.
- Expert Deceiver: He is notably clever and skilled in deceiving and misdirecting through several means, most notably with his Richard Brook persona, who managed to lead people to believe that Sherlock's a fraud, and was able to lead his assassins and clients to go after a non-existent key-code.
- Expert Networker: He was shown time and again to be an expert at managing the web of criminals he led, and he was able to consult and command all of them flawlessly, including a centuries-old Chinese crime syndicate, the Tong, showing that his criminal network encompasses worldwide, even reaching the isolated nation of North Korea.
Sherlock Holmes appears to be the only person who can keep Moriarty entertained. Moriarty reveals several unstable musings of his to Sherlock: he ponders suicide because he is bored with the world, and he is obsessed with the consulting detective until he believes Sherlock is just "another ordinary person". When Sherlock spots the hole in Moriarty's plan, Moriarty seemingly kills himself so as to have the last laugh. In their interactions (and in his interactions with any character so far), Moriarty persists in playing his games on his own terms.
Moriarty nicknames Sherlock "the virgin," and continuously interferes with his life, if only to watch him dance. On the few occasions they meet, Moriarty usually speaks to Sherlock casually while issuing threats to his friends. He displays a sick and twisted demeanour in Sherlock's company, and will do anything to win a game once he starts to play.
Irene Adler was one of Moriarty's clients. He is one of the few people in the series that have openly threatened her and it appears as though he is the only one who got away with it. He threatened to "skin her" and "make [her] into shoes" if she lied to him, and at the same time, he also gave her advice on how to manipulate Sherlock and Mycroft Holmes. 
While posing as Richard Brook, Moriarty used the information he'd gathered on Sherlock to defile the consulting detective's name in the media. It is revealed that he gained this information from Mycroft Holmes, whom he nicknamed "The Iceman". Mycroft was the only person who could elicit any sort of response from Moriarty when he had him imprisoned secretly.  When Moriarty returns, Mycroft displays signs of intimidation that he has only revealed when Sherlock mentions Charles Magnussen and when Irene Adler is presumed dead. 
Molly and Moriarty dated briefly. She describes their meeting as an "office romance," although Moriarty was posing as an IT worker at the time. He did this to get close to her and, through doing so, meet with Sherlock Holmes. She is furious when Sherlock says Jim's gay, although she seems a lot more angry at Sherlock for saying so, as opposed to Jim for flirting with him. They break up some time afterwards. Sherlock then finds Moriarty, who mocks him for falling for the gay act. 
Molly was not told until later on that Jim was Moriarty, as she is flustered when Sherlock brings up her old boyfriend when he and John Watson approach her as fugitives. Although they separated and Moriarty was taken to court for committing the "crime of the century", it appears she remained in the dark until this moment. 
Molly's blog has shed some light upon their brief relationship.
The serial killer, Jeff Hope, was sponsored to kill by Moriarty, who made it so the more people he killed, the more money his children would receive upon his death. Hope refused to speak his name until Sherlock stomped on his bullet wound before he died. This was the first incident that alerted Sherlock to Moriarty's interference.
Jim Moriarty is a consulting criminal who plans out and arranges for crimes to take place. People contact him and pay him in exchange for planning out "perfect" crimes for their personal benefit. His area of expertise ranges from faking one's own death to art forgery. He is cautious to never communicate to his clients directly as to avoid being identified, often just leaving them with his name as the only thing they know about him.
- Sponsored Jeff Hope to start killing
- Helped smuggle Black Lotus agents into London
- Faked the death of Ian Monkford
- Supplied poison to Raoul de Santos to help in the murder of Connie Prince
- Helped Miss Wenceslas in faking the authenticity of the Vermeer painting
- Advised Irene Adler on how to manipulate Sherlock and Mycroft Holmes
- Leaked information to a terrorist cell about a US/UK counter-terrorist operation
Due to his interest in Sherlock Holmes, Moriarty caught Eurus Holmes's notice and was asked by her to Mycroft for five minutes of unsupervised conversation together. At Sherrinford, Eurus mentioned 'Redbeard' to Moriarty and, from then, hatched their respective games for Sherlock. Moriarty thought Eurus to be a clever girl and supported her plans for Sherlock, Mycroft, and John by contributing recordings of himself and his image for Eurus to utilize after his death for her games.
- "Jim Moriarty. Hi!"
- ―Moriarty introducing himself in "The Great Game".
- "I've given you a glimpse, Sherlock, just a teensie glimpse of what I've got going on out there in the big bad world. I'm a specialist, you see? Like you."
- ―Moriarty in "The Great Game".
- "No one ever gets to me...and no one ever will."
- ―Moriarty in "The Great Game".
- "The flirting's over, Sherlock, daddy's had enough noooooow."
- ―Moriarty to Sherlock in "The Great Game".
- "That's what people DO!"
- ―Moriarty to Sherlock in "The Great Game".
- "If you don't stop prying...I'll burn you. I'll burn the HEART out of you."
- ―Moriarty to Sherlock in "The Great Game".
- "No you won't!"
- ―Moriarty teasing Sherlock before leaving the pool in "The Great Game".
- "Sorry boys, I'm so changeable!"
- ―Moriarty to Sherlock and Watson in "The Great Game".
- "You can't be allowed to continue. You just can't. I would like to convince you but...everything I have to say has already crossed your mind!"
- ―Moriarty quoting his literary counterpart in "The Great Game".
- "If you have what you say you have, I'll make you rich. If you don't, I'll make you into shoes."
- ―Jim Moriaty to Irene Adler, "A Scandal in Belgravia".
- "No. Sorry... Wrong day to die!"
- ―Moriarty walking away from Sherlock Holmes at the start of A Scandal in Belagravia.
- "No rush."
- ―Moriarty to the police force in "The Reichenbach Fall".
- "In a world of locked rooms, the man with the key is king, and honey you should see me in a crown!"
- ―Moriarty to Sherlock in "The Reichenbach Fall".
- "I want to solve problems... our problem. The Final Problem. It's gonna start very soon, Sherlock... the Fall. But don't worry: falling's just like flying, except there's a more permanent destination."
- ―Moriarty to Sherlock in "The Reichenbach Fall".
- "I owe you a fall, Sherlock. I. Owe. You."
- ―Moriarty to Sherlock in "The Reichenbach Fall".
- "Well, here we are at last. You and me, Sherlock. And our problem, our final problem...Stayin' alive... So boring, isn't it? Just staying...all my life I've been looking for distraction. You were the best of distraction, and now, I don't even have you. Because I've beaten you. And you know what? In the end, it was easy. Yeah...t'was easy...now I have to go back to play with the ordinary people...turns out YOU'RE ordinary, like all of them! Oh well..."
- ―Moriarty to Sherlock in "The Reichenbach Fall".
- "No...you're not ordinary...you're me...you're me!! Thank you, Sherlock Holmes. 'Thank you! Bless you. As long as I'm alive, you can save your friends. You've got a way out...well good luck with that!"
- ―Moriarty's 'last words' before shooting himself in "The Reichenbach Fall".
"You always feel pain, Sherlock...but you don't have to FEAR it!!"
__Moriarty to Sherlock in "His Last Vow"
- ""You're insane." "You're just getting that now?""
- ―Sherlock to Moriarty in "The Reichenbach Fall".
"Dead is the new sexy!"
- Moriarty towards Sherlock while licking a gun in "The Abominable Bride".
- "Did you miss me?"
- ―Moriarty in "His Last Vow".
- "Red alert! Red alert! Big, red, bouncy red alert! Klingtons attacking lower deck! Also cowboys in black hats! Darth Vader! Don't worry, I'm here now! Did you miss me? Did you miss me? Did you miss me? Miss me? Miss me? Miss me?"
- ―Gibberish Moriarty recorded for Eurus
- Moriarty can be seen wearing a fox pin on his tie on several occasions. In Grimm's Fairy Tales, there is a story called The Wedding of Mrs. Fox which involves a male fox who fakes his own death. Moriarty also showed Sherlock an envelope with Grimm's Fairy Tales.
- His ringtone is "Stayin' Alive", by the Bee Gees.
- Moriarty's favourite composer is Johann Sebastian Bach.
- The song playing while Moriarty is robbing The Tower of London in "The Reichenbach Fall" is "La gazza ladra" by Gioachino Rossini.
- Series Three's second episode "The Sign of Three" and Series Four's second episode "The Lying Detective" are the only episodes in the series where Moriarty isn't either mentioned, appears or gets alluded to.
- Series Four's third episode "The Final Problem" makes reference to Moriarty possibly having a brother who works as a station master. This is an allusion to Colonel James Moriarty, who is mentioned in the original Cohan Doyle stories The Adventure of the Final Problem and The Valley of Fear.
- The song playing while Moriarty arrives Sherrinford in "The Final Problem" is "I Want to Break Free" by Queen.
- It is said in Sherlock: The Casebook, that Moriarty was born in 1976.
- "The Abominable Bride" (Sherlock's Mind Palace)
- Thompson, Steve (writer) & Haynes, Toby (director). (15 January, 2012). "The Reichenbach Fall". Sherlock (2010). Series 2. Episode 3. BBC One.
- Gatiss, Mark (writer) & McGuigan, Paul (director). (8 August, 2010). "The Great Game". Sherlock (2010). Series 1. Episode 3. BBC One.
- Moffat, Steven (writer) & McGuigan, Paul (director). (25 July, 2010). "A Study in Pink". Sherlock (2010). Series 1. Episode 1. BBC One.
- Thompson, Steve (writer) & Lyn, Euros (director). (1 August, 2010). "The Blind Banker". Sherlock (2010). Series 1. Episode 2. BBC One.
- Moffat, Steven (writer) & McGuigan, Paul (director). (1 January, 2012). "A Scandal in Belgravia". Sherlock (2010). Series 2. Episode 1. BBC One.
- Gatiss, Mark (writer) & McGuigan, Paul (director). (8 January, 2012). "The Hounds of Baskerville". Sherlock (2010). Series 2. Episode 2. BBC One.
- Gatiss, Mark (writer) & Lovering, Jeremy (director). (1 January, 2014). "The Empty Hearse". Sherlock (2010). Series 3. Episode 1. BBC One.
- Moffat, Steven (writer) & Hurran, Nick (director). (12 January, 2014). "His Last Vow". Sherlock (2010). Series 3. Episode 3. BBC One.
- "The Abominable Bride"
- "The Final Problem (Sherlock)"
|Sherlock Holmes (Benedict Cumberbatch) • John Watson (Martin Freeman) • Mycroft Holmes (Mark Gatiss) • Jim Moriarty (Andrew Scott) • Greg Lestrade (Rupert Graves) • Molly Hooper (Louise Brealey) • Mrs Hudson (Una Stubbs)|
|Irene Adler • Mary Watson • Charles Augustus Magnussen • Eurus Holmes|
|"A Study in Pink" • "The Blind Banker" • "The Great Game"|
|"A Scandal in Belgravia" • "The Hounds of Baskerville" • "The Reichenbach Fall"|
|"The Empty Hearse" • "The Sign of Three" • "His Last Vow"|
|"The Six Thatchers" • "The Lying Detective" • "The Final Problem"|
|Unaired Pilot • "Many Happy Returns" • "The Abominable Bride"|
|"Sherlock: The Network" • Manga|