Christopher John Reuel Tolkien was born on November 21, 1924, to John Ronald Reuel Tolkien and Edith Mary Tolkien, their third and youngest son. He taught at Oxford University, where his father was a professor, and was the sole literary executor of his father's works, which he edited and provided commentary on.

He is best known for editing 24 volumes based on his father's posthumously published work, including The Silmarillion and the 12-volume series The History of Middle-Earth, a task that took 45 years. He also drew the original maps for his father's fantasy novel The Lord of the Rings, which he signed C. J. R. T., with the "J" standing for John, a baptismal name that he did not ordinarily use.

Outside his father's unfinished works, Christopher edited three tales by Geoffrey Chaucer (with Nevill Coghill) and his father's translation of Sir Gawain and the Green Knight. Tolkien scholars have remarked that he used his skill as a philologist, demonstrated in his editing of those medieval works, to research, collate, edit, and comment on his father's Middle-earth writings exactly as if they were real-world legends. The effect is both to frame his father's works and to insert himself as a narrator. They have further noted that his additions to The Silmarillion, such as filling in gaps and composing the text in his own literary style, place him as an author as well as an editor of that book.