In Greek mythology, Thalia or Thaleia (// or //; Greek: Θάλεια Tháleia, "the joyous, the abundance", from θάλλειν / thállein, "to flourish, to be green") was a nymph daughter of Hephaestus. She was also given as an anthropomorphic secondary deity of plant life and shoots, possibly as the culmination of the transmission of knowledge on volcanic ash's use as a fertiliser, characteristic of ancient viticulture in volcanic soils such as those of the island of Santorini.
Macrobius's Saturnales (song V) states how Zeus seized this Thalia whilst he was in the form of an eagle, as he did with Aegina, Leto and Ganymede. He then made love to her near the river Symethe on Sicily. She buried herself in the ground to avoid Hera's jealousy. Her twin children, the Palici, were thus born under the earth, though other authors make the Palici the sons of Hephaestus or Adranus.