The Ainur (singular: Ainu) are the immortal spirits existing before the Creation in J. R. R. Tolkien's fictional universe. These were the first beings made of the thought of Eru Ilúvatar. They were able to sing such beautiful music that the world was created from it.

The Silmarillion is a book consisting of a collection of myths and stories in varying styles by the English writer J. R. R. Tolkien. It was edited and published posthumously by his son Christopher Tolkien in 1977, assisted by Guy Gavriel Kay, who became a fantasy author. It tells of Eä, a fictional universe that includes the Blessed Realm of Valinor, the ill-fated region of Beleriand, the island of Númenor, and the continent of Middle-earth, where Tolkien's most popular works—The Hobbit and The Lord of the Rings—are set. After the success of The Hobbit, Tolkien's publisher, Stanley Unwin, requested a sequel, and Tolkien offered a draft of the writings that would later become The Silmarillion. Unwin rejected this proposal, calling the draft obscure and "too Celtic", so Tolkien began working on a new story that eventually became The Lord of the Rings.