Chistopher Tolkien was born in Leeds, England, the third son of J. R. R. Tolkien. He was educated at the Dragon School in Oxford and then at the Oratory School. During World War II, he served as a pilot in the Royal Air Force, after which he read English at Oxford University.
Young Christopher had long been part of the critical audience for J. R. R.'s fiction, first as a child listening to tales of Bilbo Baggins, and then as a teenager and young adult offering much feedback on The Lord of the Rings during its fifteen-year gestation. Christopher himself had the task of interpreting his father's sometimes self-contradictory maps of Middle-earth in order to produce the versions used in the books. Christopher re-drew the main map in the late 1970s to clarify the lettering and correct some errors and omissions.
Later the son followed in his father's footsteps, becoming a lecturer and tutor in English language at New College, Oxford from 1964 to 1975.
J. R. R. had written a great deal of material connected to the Middle-earth mythos that was not published in his lifetime; although he had originally intended to publish The Silmarillion along with The Lord of the Rings, and parts of it were in a finished state, he died in 1973 with the project unfinished.
After his father's death, Christopher embarked on organizing the masses of his father's notes, some of them written on odd scraps of paper a half-century earlier. Much of the material was handwritten, frequently a fair draft was written over a half-erased first draft, and names of characters routinely changed between the beginning and end of the same draft. Deciphering this was an arduous task, and perhaps only someone with personal experience of J. R. R. and the evolution of his stories could have made any sense of it; even so, Christopher has admitted to having to occasionally guess at what his father intended.
Nevertheless, working with Guy Gavriel Kay, he was able to publish The Silmarillion in 1977. This was followed by Unfinished Tales in 1980, and then the twelve volumes of The History of Middle-earth between 1983 and 1996, and the three volumes of the Great Tales between 2007 and 2018. He also edited several other volumes of his father's writings.