Clytia or Clytie was a water nymph, daughter of Oceanus and Tethys in Greek mythology. She loved Helios.
Helios, having loved her, abandoned her for Leucothea and left her deserted. She was so angered by his treatment that she told Leucothea’s father, Orchamus, about the affair. Since Helios had defiled Leucothea, Orchamus had her put to death by burial alive in the sands. Clytie intended to win Helios back by taking away his new love, but her actions only hardened his heart against her. She stripped herself and sat naked, with neither food nor drink, for nine days on the rocks, staring at the sun, Helios, and mourning his departure. After nine days she was transformed into the turnsole (which is known for growing on sunny, rocky hillsides), which turns its head always to look longingly at Helios’ chariot of the sun. The episode is most fully told in Ovid, Metamorphoses iv. 204, 234-56.
Modern traditions substitute the turnsole with a sunflower, which is also known for turning in the direction of the sun.
Tournesol means sunflower in french.