The History of Middle-earth is a 12-volume series of books that collect and analyse material relating to the fiction of J. R. R. Tolkien, compiled and edited by his son, Christopher Tolkien. Some of the content consists of earlier versions of already published works, while other portions are new material. These books are extremely detailed, to the point of documenting scraps of paper that have been erased multiple times with many footnotes. Christopher Tolkien has documented the history of the writing of the Middle-earth stories in as much detail as his father documented the fictional history of Middle-earth itself.

The first five books track the early history of The Silmarillion, but then discussion of the Silmarillion is postponed until part ten. Books six through nine discuss the development of The Lord of the Rings, book nine's second half discussing the Númenor story (the first versions of which were covered in Book Five). Book ten and eleven discuss the Annals of Beleriand and Annals of Aman, which are works which were developed together with the Silmarillion tradition and which also served as source material for the published Silmarillion. Book twelve discusses the development of the Appendices to The Lord of the Rings, followed by some assorted essays from Tolkien's last years of life.

1. The Book of Lost Tales 1 (1983)
2. The Book of Lost Tales 2 (1984)
3. The Lays of Beleriand (1985)
4. The Shaping of Middle-earth (1986)
5. The Lost Road and Other Writings (1987)
6. The Return of the Shadow (The History of The Lord of the Rings v.1) (1988)
7. The Treason of Isengard (The History of The Lord of the Rings v.2) (1989)
8. The War of the Ring (The History of The Lord of the Rings v.3) (1990)
9. Sauron Defeated (The History of The Lord of the Rings v.4) (1992)
10. Morgoth's Ring (The Later Silmarillion v.1) (1993)
11. The War of the Jewels (The Later Silmarillion v.2) (1994)
12. The Peoples of Middle-earth (1996)

A thirteenth volume was published in 2002, The History of Middle-earth: Index. This book has completely integrated all the indices from the books in one large index.