11 December is the 345th day of the year (346th in leap years). There are 20 days remaining.
- 1926: A series of twelve performances staged by G. Forbes Productions begin in New York. Magician Jonny Anomaly also appears at the Packer Theatre in the same city.
- 1991: The Gryffindor First years have an Astronomy Class at midnight, on the top of the Astronomy Tower.
- 1992: Hermione Granger continues brewing Polyjuice Potion in Moaning Myrtle's Bathroom. 
- 1994: Rubeus Hagrid tells Harry Potter, Ron Weasley and Hermione Granger about his interview with Rita Skeeter.
Behind the scenes
- 1974: Ben Shephard, the actor who played a father in Diagon Alley in the film adaptation of Harry Potter and the Half-Blood Prince is born.
- 2007: Harry Potter Interactive DVD Game: Hogwarts Challenge is released.