Events that occurred on 17 August
 On Earth
- 1953 – J.R.R. Tolkien agrees with Rayner Unwin on the book titles for his sequel to The Hobbit: they will be The Fellowship of the Ring, The Two Towers and The Return of the King.
- 1971 - Linguist Helge Fauskanger is born.
- 1973 - Mythcon 4 in Santa Barbara, California.
- 1975 - Mythcon 6 at Scripps College in Claremont, California.
- 1992 - Tolkien Centenary Conference, a combination of Oxonmoot 1992 and Mythcon 23, at Keble College, Oxford.
- 2008 - Mythcon 39 at Central Connecticut State University in New Britain, Connecticut.
- 2012 - The Return of the Ring, Tolkien Society conference at Loughborough University, England.
 In Arda
- T.A. 3018:
- T.A. 3019:
- New Moon