Eru Ilúvatar is the creator of the fictional world described in J.R.R. Tolkien’s The Silmarillion.
In Tolkien’s mythology, Eru Ilúvatar is the supreme being and the source of creation. He brings the Ainur into existence and gives them the Great Music, through which the plan of the world is expressed. The physical world, Arda, is then made real through this creative order.
The name combines “Eru,” meaning “The One,” with “Ilúvatar,” meaning “All-father” in Tolkien’s invented terminology. Eru is therefore distinct from the Valar, who are powerful beings within creation rather than its ultimate creator.
Melkor, later called Morgoth, is the strongest of the Ainur who rebels against Eru’s purposes. Manwë is the chief of the Valar, and Aulë is a Vala associated with craftsmanship. Those figures are important, but none is the creator of Arda.