Events that occurred on 21 August
 On Earth
- 1917 - Edith Tolkien writes a letter to her husband before leaving Withernsea for Cheltenham.
- 1954 - J.R.R. Tolkien writes a letter to Nevill Coghill.
- 1957 – Artist John Howe is born.
- 1961 – An interview with J.R.R. Tolkien ("Den besynnerlige professor Tolkien") is published in Swedish.
- 1982 – The sixth episode of the new version of the 1981 radio series of The Lord of the Rings is aired on BBC Radio 4.
- 1986 – The Shaping of Middle-earth is published in the UK.
- 1992 – Tolkien Centenary Conference, a combination of Oxonmoot 1992 and Mythcon 23, at Keble College, Oxford.
- 2000 – Mythcon 31 in Hawaii.
- 2006 – The Oxford Tolkien Conference at Exeter College, Oxford.
- 2007 – The tenth book of The Lord of the Rings Online: Shadows of Angmar, "The Hidden Hope", is released in North America.