Which Tolkien work contains the creation story known as the Ainulindalë?

The Silmarillion contains the creation story known as the Ainulindalë.

The Ainulindalë is the opening section of The Silmarillion, Tolkien’s mythology of the world of Arda. It describes Ilúvatar, the supreme creator, bringing the Ainur into being and teaching them musical themes. Their music becomes a vision of the world, which Ilúvatar then makes real.

Melkor, the greatest of the Ainur, introduces discord into the music. His rebellion foreshadows the conflicts that shape the history of Middle-earth. The section therefore establishes both creation and the presence of evil within the wider mythology.

The Silmarillion was published posthumously in 1977, edited by Tolkien’s son Christopher Tolkien. It is not a conventional single novel: it combines mythic history, genealogies, annals, and narrative tales. Unfinished Tales contains related material, but it does not contain the Ainulindalë as the opening creation account.