How’s that for a nice, searchable title? Welcome, random Googlers! There are spoilers here aplenty, so consider yourselves warned.
Cinnamon Gurl challenged me to identify the MBTI personality types of the major characters in the Harry Potter series, and that’s the kind of invitation that I just can’t refuse. First, a primer on the David Keirsey version of the system:
There are four kinds of people: (1) SJs, the joiners and club-builders – the ones who respect authority and play well with others; (2) SPs, the rebels and performers – spontaneous, charming, often very funny; (3) NFs, idealistic dreamers who thrive on imagination and romance; and (4) NTs, rational thinkers who are eminently logical.
The Harry Potter series is all about the SJs and SPs, concrete thinkers who either follow the rules (SJ) or break them (SP). On the whole, Rowling seems to side with the SPs. Everything in the wizarding world is concrete, even the magic (especially the magic). Wizards don’t read novels – or write them. At best they read the occasional fairy tale, but Beedle the Bard appears to be the only wizard who ever had a literary imagination. Wizards are scientists: they combine ingredients to create potions, they care for magical plants and creatures, and they utter set incantations to create particular effects. There is some innovation in the wizarding world (particularly by the Half-Blood Prince), but little true creativity. Perhaps if we’d ever followed Hermione to Arithmancy class or hung out in the Ravenclaw common room we might have met a few NTs, but NF idealists are terribly thin on the ground.
The classic SPs of the series are Fred and George Weasley. They are pranksters and jokers, latter-day versions of their rebellious forebears, Prongs and Padfoot. They are natural entrepreneurs with plenty of skill and intelligence but little tolerance for structured education. No matter how much Molly Weasley pressures them, they will never fit into the Ministry of Magic, being far better suited to throwing Dungbombs at authority figures than to obeying or becoming them.
Harry himself is an SP, though in far less spectacular style than the Weasley twins: he might well be an ISTP with his natural athletic skill and his ability to lie low when necessary. He is naturally ruled by impulse and though he is capable of planning and executing a strategy, he usually prefers flying by the seat of his pants. Bravery is a core value for Rowling, and it is an attribute that comes most naturally to SPs with their physical courage, their quickness of impulse, and their lack of debilitating factors like an uncomfortably vivid imagination.
Ranged against the SPs are a host of evil SJs. The series begins with Vernon Dursley’s irritable suspicion of anything that defies his definition of normal; he prides himself upon his pack mentality and his cookie-cutter suburban lifestyle. His counterparts in the wizarding world are Percy Weasley and Dolores Umbridge, both of whom are consummate rule-makers and enforcers. Though Percy proves to be redeemable in the end, his worst traits all arise from his SJ infatuation with status, authority, and conformity. There are many other, more moderate, SJs in the series: Molly Weasley, Professor McGonagall, and minor student characters like Lavender Brown (with her trademark giggles and consummately normal girly silliness). Draco Malfoy is probably an SJ as well, though in his case his SJ characteristics don’t actually make him go evil (he is that way already by heredity).
The SJs are redeemed primarily by Hermione, a classic ESTJ whose respect for rules and authority is corrupted sufficiently by Ron and Harry to become a useful counter-balance to their occasional recklessness. Hermione is supremely organized, a careful planner who can juggle everything from an unprecedentedly full timetable to packing a bottomless backpack with everything needed for a winter-long camping trip. She always urges Harry to stick to the task Dumbledore has set for him, and she is least moved by doubts or hesitations, providing a backbone when Harry and Ron lose their resolve.
NT students are hard to find a Hogwarts: in the Muggle world they’re easily located by their D&D clubs, their gaming conventions, and their science fair projects. There seem to be no nerds at Hogwarts, no cliques of misfits who bond over their arcane interests. Neville’s flair for Herbology suggests an NT nature – he may be a mild-mannered INTJ, intimidated by his robust ESTJ grandmother but never quite conforming to social expectations. Luna and Xenophilius Lovegood are mad eccentrics, a sure sign of their NT nature (all eccentrics are NTs, though not all NTs are eccentrics).
The best NTs in the Potterverse, of course, are Albus Dumbledore and Severus Snape. (Snape’s loyal following, especially in the N-dominated blogosphere, may arise from the fact that he is one of the few abstract thinkers in the concrete world of witchcraft and wizardry.) Snape is a true scientist: as the Half-Blood Prince, he tinkered with potions and created spells of his own invention. The only wizard who surpasses him for intellect and creativity is Dumbledore. His early friendship with Grindelwald – based on a shared intellectual vision – suggests to me that he is a classic NT, probably an ENTP or an INTP. Dumbledore’s quirky sense of humour, his flair for nonsense, and his unsurpassed magical knowledge all place him in the same category as Lewis Carroll, Albert Einstein, and Jon Stewart.
Perhaps the only NF in the series is Lily Potter. Against the advice of her friends, she remains loyal to Snape even though he’s an outsider and a Slytherin. She is impervious to peer pressure but not to her own ideals: when Snape goes over to the Death Eaters, she ends the friendship. Lily is described by Slughorn as an intuitive potion-maker, someone with good instincts and an ability to follow them. She harnesses the power of love so skillfully that she helps defeat the greatest wizard in the world; she also has a weak spot for a good-looking Quidditch player whose arrogance cannot conceal his romantic interest. She is credulous and even, at times, naïve: she considers Wormtail a safe repository for secrets and laughs away the suggestion that Dumbledore might ever have been friends with Grindelwald.
The only other potential NF I can think of is Remus Lupin: his life is one of tortured emotion – he is an outcast who falls in love, considers abandoning his child out of a misguided sense of duty, and ultimately gives his life for a good cause. R.I.P., Remus. We hardly knew ye.
Final Tally:
SPs: Harry Potter, James Potter, Sirius Black, Mad-Eye Moody (though he might be an NT: much depends on how accurate Barty Crouch’s impersonation was), Mr. Weasley, Fred and George Weasley (and possibly Charlie, Bill, and Ron as well, though with their prefect badges an argument could be made for SJ status), Ginny Weasley.
SJs: Hermione Granger, Percy Weasley, Cornelius Fudge, Horace Slughorn, Hagrid, Molly Weasley, Dolores Umbridge, Minerva McGonagall, the entire Hufflepuff house (with their virtues of loyalty and industry), the Dursleys, the Patil twins, Lavender Brown, Draco Malfoy, Crabbe and Goyle (obedient henchmen just looking for a gang to join).
NTs: Neville Longbottom, Luna and Xenophilius Lovegood, numerous unnamed Ravenclaws (though not Cho Chang, who is too vacuous to be anything but an SJ), Phineas Nigellus Black, Severus Snape, Albus Dumbledore, probably Voldemort (though there’s so little left of his soul that it’s hard to tell).
NFs: Lily Evans Potter, Remus Lupin.
Did I leave anyone out?
(Just before hitting "publish" I did a quick search and found this MBTI-based "Which Harry Potter Character Are You?" quiz. You can see all the possible results here. I agree with many of them, though I think the selection is likely slanted by the need to select a reasonably high-profile character for each of the 16 types. And even then the best they could do for an ENFJ was Olympe Maxime!

Harry Potter Personality Quiz by Pirate Monkeys Inc.I still think Dumbledore's an NT - but as a potentially-fellow INFJ, I'm prepared to be persuaded otherwise.)