Events that occurred on 11 September.
 On Earth
- 1918 - J.R.R. Tolkien is transferred to Savoy Convalescent Hospital, Blackpool, west coast of England.
- 1951 - Second day of the Congrès Internationale de Philologie Moderne at the University of Liège, a conference in which J.R.R. Tolkien delivers the paper "Middle English 'Losenger'".
- 1955 - J.R.R. Tolkien writes Letter 169.
- 1957 - J.R.R. Tolkien writes Letter 202.
- 1957 - The Oxford Mail reports from the International Fantasy Award, won by Tolkien.
- 1959 - J.R.R. Tolkien writes Letter 217.
- 1964 - J.R.R. Tolkien writes Letter 264.
- 1967 - J.R.R. Tolkien writes Letter 298.
- 1970 - J.R.R. Tolkien writes Letter 316.
- 1982 - The ninth episode of the new version of the 1981 radio series of The Lord of the Rings is aired on BBC Radio 4.
- 2006 - Translator William Auld dies.
- 2010 - Bulgarian Tolkien Society's 6th Tolkien-Fest in Sofia.
- 2014 - Oxonmoot 2014 at Lady Margaret Hall.
- 2015 - Oxonmoot 2015 at St Antony's College.
- 2016 - Oxonmoot 2016 at St Antony's College.
 In Arda
- T.A. 3018: