Lúthien and Beren are characters in J. R. R. Tolkien's fantasy world Middle-earth. Lúthien is an elf, daughter of the elf-king Thingol and goddess-like Melian. Beren is a mortal man. The complex tale of their love for each other and the quest they are forced to embark upon is a story of triumph against overwhelming odds but ending in tragedy. It appears in The Silmarillion, the epic poem The Lay of Leithian, the Grey Annals section of The War of the Jewels, and in the texts collected in the 2017 book Beren and Lúthien. Their story is told to Frodo by Aragorn in The Lord of the Rings.

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.