Events that occurred on 31 August
 On Earth
- 1937 - J.R.R. Tolkien writes Letter 15.
- 1938 - J.R.R. Tolkien writes Letter 33.
- 1938 – J.R.R. Tolkien submits the finished version of Farmer Giles of Ham to Allen and Unwin, but it is rejected.
- 1962 - Voice actor Dee Bradley Baker is born.
- 1980 - Amon Hen 46 is published.
 In Arda
Note: Months of the Shire Calendar only have 30 days, so no events have nor will happen on the 31st.