Gryffindor values courage, chivalry and boldness. Its emblematic animal is the lion and its colours are scarlet and gold. Minerva McGonagall is the most recent Head of House. Nearly Headless Nick is the house ghost. The founder of the house is Godric Gryffindor.

As this is the house to which Harry Potter belongs, its private quarters are the only ones that have been described in any detail (though Slytherin's common room was described briefly in Harry Potter and the Chamber of Secrets), and its members tend to get the most attention. These are located in one of the castle's towers, the entrance to which is located on the seventh floor and is guarded by a painting of the Fat Lady, who is garbed in a pink dress. She permits entry only after being given the correct (regularly changing) password. Behind her is a large common room, with a fireplace, and two staircases leading up to the boys' and girls' dormitories.

According to J. K. Rowling, Gryffindor corresponds roughly to the element of fire, which may partly be the reason for its colours.

It must be remembered that since Harry Potter is a Gryffindor, it receives the most favourable depiction.

Gryffindors are disliked by Houses such as Slytherin, according to Phineas Nigellus Black, because they apparently engage in pointless heroics. There might also be an element of jealousy; since the arrival of Harry Potter, Gryffindor has received a certain amount of publicity that they hadn't had before. Harry and his fellow Gryffindors tend to win in a lot of circumstances which, when viewed from a Slytherin's point of view, may be considered unfair. Examples of this include the last minute points awarded by the Headmaster, Professor Dumbledore, at the end of term feast, which conveniently put Gryffindor ten points ahead of Slytherin or when Harry gets special permission from Professor McGonagall to have his own broomstick for the Gryffindor Quidditch team, even though first years are not permitted their own broomstick (Harry Potter and the Philosopher's Stone). Another example is when Harry Potter is chosen as the fourth competitor in the Triwizard Tournament, and is accused of cheating, stealing Cedric Diggory's thunder and craving attention.

A few notable Gryffindors (for a complete list, see List of characters in the Harry Potter books):

Like Salazar Slytherin, its founder, Slytherin house values ambition, cunning and resourcefulness. Its emblematic animal is the serpent, and its colours are green and silver. Professor Horace Slughorn is the Head of Slytherin, replacing Severus Snape, who as well, replaced Slughorn when he retired for the first time several years ago. The Bloody Baron is the house ghost. According to Rowling, Slytherin corresponds roughly to the element of water^{[citation needed]}. The Slytherin dormitories and common room are reached through a bare stone wall in the dungeons. The Slytherin common room is a long, low underground room (probably under the Hogwarts lake, thus Slytherin house's affiliation with water) with rough stone walls and round greenish lamps hanging from the ceiling.

The Sorting Hat claims that blood purity is a factor in selecting Slytherins, although this is not mentioned until the fifth book. This suggests that it bases its decisions more upon the views of its members, than directly on any accurate test of blood. There is no reason to believe that muggle-born students are not sorted there, merely that pure-blooded students are more desirable to that house. There are definite examples of half-bloods in the house (Snape, Voldemort), and one notable example of a non-pureblood who was nearly sorted into the house (Harry Potter). The fact that Rowling intended to place a character named Mafalda, a half-blood who was the daughter of a Squib and a Muggle, in Slytherin, suggests that Rowling at least does not view the Slytherin House desire for blood-purity as particularly influential upon the Sorting Hat. Mafalda, intended to be a cousin of the Weasley children, was ultimately cut from final edits of the book, to allow for more room to develop other plot lines[2].

According to Albus Dumbledore (in 'The Chamber of Secrets'), the qualities which "Slytherin prized in his hand-picked students" include "Parseltongue...resourcefulness...determination...a certain disregard for the rules": which Dumbledore notes are qualities possessed by Harry Potter.

Contrary to the wishes of the other founders, Salazar Slytherin wanted a stricter policy of admittance—one limited to pure-blood students. The controversy this created apparently led to Salazar leaving the school and the Chamber of Secrets behind. A millennium later, the house's students are still considered affiliated with Salazar's reputed views although some half-bloods, most notably Voldemort and Snape, have been in Slytherin. "Pureblood" lineage is certainly one of Voldemort's public goals. It is often mentioned in the novels (especially in Philosopher's Stone and Chamber of Secrets) that most of the dark wizards were in Slytherin (though how many were from this house before Tom Marvolo Riddle began recruiting there is unstated: as his own House, it was certainly most easy for him to recruit there). However, good Slytherin wizards also exist: most notable in the canon is Horace Slughorn, a member of the House prior to the entry of Tom Riddle. Cunning and ambition are easily turned towards ill purposes, but are not inherently negative; furthermore, daring, intelligence, and loyalty can as easily become negative. A reason Slytherins may not be thought of as the best kind of people is because they value their own lives more than the lives of others. When Harry is trying to run away, because he is afraid that his presence is putting his friends' lives in danger in Chapter 23 of Harry Potter and the Order of the Phoenix, Phineas Nigellus sees him and says, "We Slytherins are brave, yes, but not stupid. For instance, when given the choice, we will always choose to save our own necks." Rowling herself has defended Slytherins, claiming that while most Dark wizards are Slytherins, most Slytherins are not Dark, and smaller groups of Voldemort's supporters are aligned with other Houses.

A few notable Slytherins (for a complete list, see List of characters in the Harry Potter books. Also see Minor Slytherins):

• Tom Riddle/Lord Voldemort
• Draco Malfoy and the rest of the Malfoy family
• The Black family (with the exception of Sirius Black)
• Other Slytherins in Harry Potter's year (Vincent Crabbe, Gregory Goyle, Pansy Parkinson, Millicent Bulstrode, Blaise Zabini, Theodore Nott, and Daphne Greengrass)
• Marcus Flint
• Bellatrix (Black) Lestrange
• Horace Slughorn
• Regulus Black
• Severus Snape
• Phineas Nigellus Black
• The House of Gaunt