Lētṓ (Greek: Λητώ, Λατώ, Lato in Dorian Greek, etymology and meaning disputed), in Greek mythology, is a daughter of the Titans Coeus and Phoebe: Kos claimed her birthplace. In the Olympian scheme of things, Zeus is the father of her twins, Apollo and Artemis, the Letoides. For the classical Greeks, Leto is scarcely to be conceived apart from being pregnant and finding a suitable place to be delivered of Apollo, the second of her twins. This is her one active mythic role: once Apollo and Artemis are grown, Leto withdraws, to remain a dim and benevolent matronly figure upon Olympus, her part already played.
In Roman mythology, Leto's equivalent is Latona, a Latinization of her name.
In Crete, at the city of Dreros, Spyridon Marinatos uncovered an eighth-century post-Minoan hearth house temple in which there were found three unique figures of Apollo, Artemis and Leto made of brass sheeting hammered over a shaped core. Walter Burkert notes (in Greek Religion) that in Phaistos she appears in connection with an initiation cult.
Leto was identified from the fourth century onwards with the principal local mother goddess of Anatolian Lycia, as the region became Hellenized. Her sanctuary, the Letoon near Xanthos, united the Lycian confederacy of city-states. The people of Kos also claimed Leto as their own. Another sanctuary, more recently identified, was at Oenoanda in the north of Lycia. There was, of course, a further Letoon at Delos.
A measure of what a primal goddess Leto was can be recognized in her father and mother. Her Titan father is called "Coeus," and his obscure name links him to the sphere of heaven from pole to pole. Leto's mother "Phoebe" is precisely the "bright, purifying" epithet of the full moon.
It is remarkable that Leto brought forth Artemis, the elder twin, without struggle or pain — as if she were merely revealing another manifestation of herself. Leto labored for nine nights and nine days for Apollo, according to the Homeric Hymn to Delian Apollo, in the presence of all the first among the deathless goddesses as witnesses: Dione, Rhea, Ichnaea, Themis and the "loud-moaning" sea-goddess Amphitrite. Only Hera kept apart, perhaps to kidnap Eileithyia or Ilithyia, the goddess of childbirth, to prevent Leto from going into labor. Instead Artemis, having been born first, assisted with the birth of Apollo. Another version states that Artemis was born one day before Apollo, on the island of Ortygia, and that she helped Leto cross the sea to Delos the next day to give birth to Apollo.
Leto was threatened and assailed in her wanderings by chthonic monsters of the ancient earth and old ways, and these became the enemies of Apollo and Artemis. One was the Titan Tityos, a phallic being who grew so vast that he split his mother's womb and had to be carried to term by Gaia herself. He attempted to waylay Leto near Delphi, but was laid low by the arrows of Apollo— or possibly Artemis, as another myth-teller recalled.
Another ancient earth creature that had to be overcome was the dragon Pytho, or Python, which lived in a cleft of the mother-rock beneath Delphi and beside the Castalian Spring. Apollo slew it but had to do penance and be cleansed afterwards, since Python was a child of Gaea. Sometimes the slaying was said to be because Python had brutally raped Leto while she was pregnant with Apollo and Artemis, but one way or another, it was necessary that the ancient Delphic Oracle pass to the protection of the new god.
A Queen of Thebes and wife of Amphion, Niobe boasted of her superiority to Leto because she had fourteen children (Niobids), seven male and seven female, while Leto had only two. For her hubris, Apollo killed her sons as they practiced athletics, with the last begging for his life, and Artemis her daughters. Apollo and Artemis used poisoned arrows to kill them, though according to some versions a number of the Niobids were spared (Chloris, usually). Amphion, at the sight of his dead sons, either killed himself or was killed by Zeus after swearing revenge. A devastated Niobe fled to Mount Sipylus in Asia Minor and either turned to stone as she wept or killed herself. Her tears formed the river Achelous. Zeus had turned all the people of Thebes to stone so no one buried the Niobids until the ninth day after their death, when the gods themselves entombed them.
Leto was intensely worshipped in Lycia, Asia Minor. In Delos and Athens she was worshipped primarily as an adjunct to her children. Herodotus reported a temple to her in Egypt supposedly attached to a floating island called "Khemmis" in Buto, which also included a temple to an Egyptian god Greeks identified by interpretatio graeca'' as Apollo. There, Herodotus was given to understand, the goddess whom Greeks recognised as Leto was worshipped in the form of Wadjet, the cobra-headed goddess of Lower Egypt.
This scene is represented in the central fountain, the Bassin de Latone, in the garden terrace of Versailles.