Prefect

A prefect at Hogwarts School of Witchcraft and Wizardry is a student who has been given extra authority and responsibilities by the Head of House and Headmaster or headmistress. One male and one female student are chosen from each house in their fifth year to act as prefects, and would continue to be prefects in their sixth and seventh years until they leave school. Thus, there are approximately six prefects per house, and twenty-four prefects in the whole school at one time. The Head Boy and Head Girl may be chosen from among this number and may not be replaced, but, like with James Potter, the Head Boy or Girl does not have to be a prefect.

Role
"I don't believe it! I don't believe it! Oh, Ron, how wonderful! A prefect! That's everyone in the family!"

- Molly Weasley

Prefects are allowed to take House points away from other students in their own house as a penalty for rule-breaking, but they are not allowed to take points from other prefects or students in other houses. Prefects can give detentions as a form of punishment.

Prefects patrol the corridors of the Hogwarts Express on the way to school and attend a meeting in a special prefects' carriage where they are instructed by the Head Boy and Girl. They also patrol hallways to ensure that other students are not breaking curfew. There is a bathroom with a large, pool-like bath on the fifth floor of Hogwarts Castle that is reserved for prefects and Quidditch captains. It is located at the fourth door to the left of the statue of Boris the Bewildered. The only known password to this bathroom is "pine fresh", which was used during the 1994–1995 school year.

Prefects have other responsibilities as student leaders. They show the first years the way to their dormitories on their first day of school at Hogwarts School of Witchcraft and Wizardry, and supervise the decorating of the castle for Christmas (and presumably other events as well). They also watch the younger students when bad weather keeps them indoors over break times.

Once a student becomes a prefect, they have a better chance of becoming Head Boy or Head Girl; however, a student is not required to earn the former honour in order to earn the latter. This fact was exemplified in the knowledge that Remus Lupin was a Gryffindor prefect but James Potter was later appointed the Head Boy.

Prefects are given a badge; the colours are the colours of the prefect's House and/or silver. They are supposed to wear the badge on their school uniform. The badge would have the letter "P" on it while the Head Boy's badge would have "Head Boy" on it, and the Head Girl's with "Head Girl". If the prefect is on his or her house Quidditch team, he or she would not be required to wear the prefect badge on their Quidditch robes.

Hermione Granger was a sensible prefect, and took the role very seriously. Ron Weasley was a little less serious about it, to the point of neglecting several rules. In fact, he was extremely surprised to be chosen as a prefect as he expected Professor Dumbledore would have chosen Harry. Dumbledore thought Harry would have too much on his mind and gave it to Ron instead. Ron received a letter from his brother Percy, stating that Ron might risk losing his badge by associating with the apparently dangerous Harry Potter. This may mean if the prefects cross a certain point of abusing their powers, they might have their position revoked.

Draco Malfoy and Pansy Parkinson abused their positions greatly, to the annoyance of Hermione Granger. In his sixth year, Draco refused to live up to his prefect duties any further, in preference of his Death Eater mission of assassinating Albus Dumbledore. This could mean that students have the right to reject the position of prefect any time they desire, or that Draco was severely punished for being irresponsible.

Hufflepuff

 * Cedric Diggory
 * Gabriel Truman
 * Ernie Macmillan
 * Hannah Abbott

Gryffindor

 * Albus Dumbledore
 * Minerva McGonagall
 * Remus Lupin
 * Bill Weasley
 * Charlie Weasley
 * Percy Weasley
 * Ron Weasley
 * Hermione Granger
 * Unidentified Gryffindor Prefect
 * Entrance Hall Gryffindor Prefect

Ravenclaw

 * Penelope Clearwater
 * Anthony Goldstein
 * Padma Patil
 * Robert Hilliard

Slytherin

 * Tom Riddle
 * Lucius Malfoy
 * Draco Malfoy
 * Pansy Parkinson
 * Gemma Farley
 * Unidentified Slytherin Prefect (I)
 * Unidentified Slytherin Prefect (II)
 * Unidentified Slytherin Prefect (III)
 * Third Floor Corridor Slytherin prefect
 * Dungeon Corridor Slytherin prefect (I)
 * Dungeon Corridor Slytherin prefect (II)

Prefects whose house is Unknown

 * Jake Flinton
 * Cyril Meakin
 * David Boorman (I)
 * Felix Brunt (I)
 * Alex Sykes (I)
 * Terry Strickland
 * Irving Cram (I)
 * Simon Dedworth (I)
 * Ross Gibberd (I)
 * Nicolas Grimmett
 * Robert Hawking
 * Eric Murley
 * Damian Perriss
 * Gordon Pummell (I)
 * Ryan Westrup
 * Ivan Renshaw (I)
 * Edmund Spiers
 * Jonathan Spratt
 * Kevin Sterndale
 * Terry Strickland
 * Mervyn Wynch

Behind the scenes

 * There was some confusion about the point-taking ability of prefects after the original release of Harry Potter and the Order of the Phoenix. It had previously been stated in Harry Potter and the Chamber of Secrets that prefects could dock points, but in a scene in the first printing of Harry Potter and the Order of the Phoenix Ron Weasley, Ernie Macmillan, and Draco Malfoy all either state outright or imply that prefects are not allowed to take points. This was pointed out as a mistake, and subsequent printings had a slightly different version of the dialogue, making it clear that prefects can take points, just not from other prefects.
 * Quidditch captains are given similar rights as the prefects, like the password to the prefect's bathroom, but are not allowed to dock points.
 * In 1994, Harry Potter first experienced using the prefects' bathroom on the fifth floor of the Hogwarts Castle. Despite the fact that he didn't have the privilege at that time, Cedric Diggory, a Hufflepuff prefect, gave him the password and permission to use it prior to the second task of the Triwizard Tournament.
 * In the film adaptation of Harry Potter and the Order of the Phoenix, the subplot of Ron and Hermione being made prefects is dropped, and is likewise omitted from the film adaptation of Harry Potter and the Half-Blood Prince.
 * In the film adaptation of Harry Potter and the Chamber of Secrets, Nathan Lubbock-Smith portrays a prefect of an unidentified house.