Elemmírë (Q, pron. [ˌelemˈmiːre]) was a Vanyarin Elf, famed for thecreation of a lament for the Darkening of Valinor, the Aldudénië. When Melkor assaulted the Two Trees, the Vanyar and other Elves of Valinor were celebrating a festival on Taniquetil, and so Elemmírë most likely personally witnessed the destruction of the Trees. The song the elf made to lament the death of the Two Trees was said to be known by all of the Eldar.
Note that the form of the word does not allow us to know whether Elemmírë was a male or a female Elf.