Phyllis (Greek: Φυλλίς) is a character in Greek mythology, daughter of a Thracian king (according to some, of Sithon; most other accounts don't give her father's name at all, but one informs that he was named either Philander, Ciasus, or Thelus). She married Demophon, King of Athens and son of Theseus, while he stopped in Thrace on his journey home from the Trojan War.
Demophon, duty bound to Greece, returns home to help his father, leaving Phyllis behind. She sends him away with a coffin with the sacrament of Rhea, asking him to open it only when he has given up hope of returning to her. From here, the story diverges. In one version, Phyllis realizes that he will not return and commits suicide by hanging herself from a tree. Where she is buried, an almond tree grows, which blossoms when Demophon returns to her. In a second version of the story, Demophon opens the caskets and, horrified by what he saw in there, rides off like wild, but his horse stumbles and he accidentally falls on his own sword.
There is also some confusion regarding which nut tree she became, as hazelnuts were long called nux Phyllidos, and are still sometimes called "filberts" today. In English, this version goes back at least to Gower, who writes in Confessio Amantis (ca. 1390):
That Phillis in the same throweWas schape into a notetre,
That alle men it mihte se,
And after Phillis philliberd
This tre was cleped in the yerd,
And yit for Demephon to schame
Into this dai it berth the name. —Book 4, Lines 866–72
This story most notably appears in the second poem of Ovid's Heroides, a book of epistolary poems from mythological women to their respective men, and it also appears in the Aitia of Callimachus.
The Nine Ways is derived from the story of Phyllis, who is said to have returned nine times to the shores to wait for Demophon's return.
"Phyllis" is commonly used as a female given name in English-speaking countries.