Events that occurred on 12 August
 On Earth
- 1911 - Voice actor Felix Felton is born.
- 1915 - J.R.R. Tolkien writes Letter 5.
- 1944 - J.R.R. Tolkien writes Letter 78.
- 1959 - J.R.R. Tolkien writes Letter 216.
- 1978 - Mythcon 9 in West Sacramento, California.
- 1983 - Mythcon 14 at Scripps College in Claremont, California.
- 1984 - Mythcon 15 at Mills College in Oakland, California.
- 2004 - Voice actor Peter Woodthorpe dies.
- 2005 - The Tolkien Society's Tolkien 2005 conference in Birmingham, England.
- 2011 - Omentielva Cantea - 4th International Conference on Tolkien's Invented Languages in Valencia, Spain.
- 2017 - Omentielva Otsea - the Seventh International Conference on Tolkien's Invented Languages at California State University, East Bay.