William is a given name that can refer to:
- William, a Pukwudgie named by Isolt Sayre
- William, a wizard who lived in the late 19th century
- William, an Occamy owned by Silvanus Kettleburn
- William III, the King of England from 1689 until his death
- William Alderton, allegedly the father of Alderton
- William Billings, a Muggle theatre director
- William Friend, an American businessman turned fraudster
- William Gallagher, a wizard reported missing in 1997
- William Sayre, the father of Isolt Sayre
- William Shakespeare, a Muggle author who wrote Hamlet
- William "Bill" Weasley, the eldest son of Arthur and Molly Weasley
Behind the scenes[]
Real-world individuals with the given name William include:
- William Green, a voice actor for the video game adaptation of Harry Potter and the Chamber of Secrets
- William Høeg, a Danish voice actor who voiced Draco Malfoy in the Danish films
- William Melling, a British actor who portrays Nigel Wolpert in the film adaptations of the Harry Potter books
- William Ross, an American composer