The Ainur (from Valarin Ayanûz; singular Ainu) are a fictional race from J. R. R. Tolkien's universe, Eä.

The Ainur are the spirits emanated by Ilúvatar to help him to create the Universe, Eä, through the Music of the Ainur. After the creation of Arda, many of the Ainur worked to guide and order its growth. Of these there were fifteen more powerful than the rest. Fourteen became the Valar. The fifteenth, Melkor, who was originally considered a Vala, became the first Dark Lord. The lesser Ainur that accompanied the Valar into Arda are known as the Maiar.