In J. R. R. Tolkien's Middle-earth, the Moriquendi — the Elves of Darkness — are, in essence, the Elves that did not join the Great March over the sea and behold the light of the Two Trees in Valinor. They lingered on the shores of Middle-earth or, indeed, never passed the Blue Mountains on the east of Beleriand or the Misty Mountains further to the east.
It is a term for Avari, Sindar, and Nandor, but in practice is only applied to the Avari.
- "Those Elves the Calaquendi call the Úmanyar, since they came never to the land of Aman and the Blessed Realm; but the Úmanyar and the Avari alike they call the Moriquendi, Elves of the Darkness, for they never beheld the Light that was before the Sun and Moon."
The term "Dark Elf" in Tolkien's writing seems to hold a special (not explained) meaning, as it is given as a special title of Eöl of Nan Elmoth.
Other dark elves from other fictional created worlds are the very different Drow elves from Dungeons & Dragons worlds of Greyhawk and the Forgotten Realms.