Hermione is a Muggle-born Gryffindor, who becomes best friends with Harry Potter and Ron Weasley. Rowling states that she was born on 19 September 1979 and she was nearly twelve when she first attended Hogwarts. She is an overachiever who excels academically and is described by Rowling as a "very logical, upright and good" character. Rowling adds that Hermione's parents, two Muggle dentists, are a bit bemused by their odd daughter but "quite proud of her all the same". They are well aware of the wizard world and have visited Diagon Alley with her. Hermione is an only child. But Rowling revealed in a 2004 interview that Hermione was originally intended to have a sister, but the planned sibling did not appear since she felt it "might be too late now" to introduce the character. Rowling has called the character of Luna Lovegood the "anti-Hermione" as they are so very different.

Rowling said the character of Hermione has several autobiographic influences: "I did not set out to make Hermione like me but she is a bit like me. She is an exaggeration of how I was when I was younger." She recalled being called a "little know-it-all" in her youth. And she says that not unlike herself, "there is a lot of insecurity and a great fear of failure" beneath Hermione's swottiness. Finally, according to Rowling, next to Albus Dumbledore, Hermione is the perfect expository character; because of her encyclopedic knowledge, she can always be used as a plot dump to explain the Harry Potter universe. Rowling also states that her feminist conscience is rescued by Hermione, "who's the brightest witch of her age" and a "very strong female character.

Hermione's first name is taken from a character in William Shakespeare's The Winter's Tale, though Rowling has said that the two characters have little to nothing in common. Rowling said that she wanted her name to be unusual since if fewer girls had the name, fewer girls would get teased for it and it seemed that "a pair of professional dentists, who liked to prove how clever they were". Her original surname was "Puckle", but Rowling felt the name "did not suit her at all", and so the less frivolous Granger was used.