What is the title of J.R.R. Tolkien’s posthumously published 1977 legendarium collection?

J.R.R. Tolkien’s posthumously published 1977 legendarium collection is The Silmarillion.

Tolkien worked on the stories and histories that became The Silmarillion for much of his life. Unlike The Hobbit, it is not a single continuous adventure novel. It presents creation myths, accounts of the Elves, the wars against Morgoth, and material connected with the later history of Middle-earth. Its opening section, the Ainulindalë, describes the creation of the world through music.

Tolkien died in 1973 without preparing the manuscript for publication. His son Christopher Tolkien edited, arranged and sometimes selected among the extensive papers, and George Allen & Unwin published the book in 1977. Readers sometimes confuse it with Unfinished Tales, another posthumous collection edited by Christopher, or with The Book of Lost Tales, an earlier phase of Tolkien’s evolving mythology. The Silmarillion is the standard title for the 1977 published work.