Events that occurred on 4 September.
 On Earth
- 1918 - J.R.R. Tolkien attends a medical board examination in Kingston-upon-Hull.
- 1936 - German translator Hans J. Schütz is born
- 1957 - J.R.R. Tolkien meets with some American producers interested in making an animated version of The Lord of the Rings (see Letter 201).
- 1960 - The Fellowship of the Ring becomes formally constituted.
- 1968 - J.R.R. Tolkien writes a letter to Mary Fairburn.
- 1970 – The first Mythcon is held at Harvey Mudd College in Claremont, California.
- 1971 - Mythcon 2 in Santa Barbara, California.
- 1982 - The eighth episode of the new version of the 1981 radio series of The Lord of the Rings is aired on BBC Radio 4.
- 2020 - A second edition of The First and Second Ages is published.