Events that occurred on 12 December.
 On Earth
- 1949 - Actor Bill Nighy is born.
- 1955 - J.R.R. Tolkien writes Letter 178.
- 1955 - J.R.R. Tolkien writes a letter to David Masson.
- 1964 - The tenth episode of the Princess-serialization of The Hobbit is published.
- 1966 - J.R.R. Tolkien writes Letter 292.
- 1967 - J.R.R. Tolkien writes Letter 299.
- 1972 - Writers for the 70's: J.R.R. Tolkien is released.
- 2011 - Update 5: Armies of Isengard, the fifth free update of The Lord of the Rings Online, is released.
- 2012 - The Hobbit: An Unexpected Journey is released in New Zealand.
- 2014 - The Hobbit: The Battle of the Five Armies is released in the United Kingdom.