In Greek mythology, Leto (Greek: Λητώ, Lato in Dorian Greek, the "hidden one") is a daughter of the Titans Coeus and Phoebe. In the Olympian scheme of things, Zeus is the father of her twins, Apollo and Artemis. 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 Mount Olympus, her part already played.
It has been proposed that the name "Leto" originates from the verb "lanthanein" (to be concealed or oblivious) hence "lethe" (oblivion) and "lotus" (the fruit that brings oblivion to those who eat it). Others say it comes from the same origin as "Leda", meaning "woman/wife" in ancient Lydia.
In Crete, at the city of Dreros, Spyridon Marinatos uncovered an 8th-century post-Minoan hearth house temple which had 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 Phaestos she appears in connection with an initiation cult.
In Roman mythology her equivalent, as mother of Apollo and Diana, is Latona.
Birth of Artemis and Apollo
When Hera discovered that Leto was pregnant and that Zeus was the father, she realized that the offspring would cement the new order. She was powerless to stop the flow of events, but she banned Leto from giving birth on "terra firma", the mainland, any island at sea, or any place under the sun (Hyginus, Fabulae, 140). Some mythographers hinted that Leto came down from the land of the Hyperboreans in the guise of a she-wolf, or that she sought out the "wolf-country" of Lycia for her denning. Most accounts agree that she found the barren floating island of Delos, which was neither mainland nor a real island, and gave birth there, promising the island wealth from the worshippers who would flock to the obscure birthplace of the splendid god who was to come. The island was surrounded by swans. As a gesture of gratitude, Delos was secured with four pillars and later became sacred to Apollo.
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.
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 hearsay of a temple to her in Egypt attached to a floating island called "Khemmis" in Buto, which also included a temple to Apollo. There, Leto was wosrhipped in the form of Wadjet, the cobra-headed goddess of lower Egypt. However, Herodotus didn't believe in the existence of either temple.
Witnesses at the birth of Apollo
According to the Homeric hymn, the goddesses who assembled to be witnesses at the birth of Apollo were responding to a public occasion in the rites of a dynasty, where the authenticity of the child must be established beyond doubt from the first moment. The dynastic rite of the witnessed birth must have been familiar to the hymn's 8th-century hearers. The dynasty that is so concerned to be authenticated in this myth is the new dynasty of Zeus and the Olympian Pantheon, and the goddesses at Delos who bear witness to the rightness of the birth are the great goddesses of the old order. Demeter is not present; her mother Rhea attends. Aphrodite, a generation older than Zeus, is not present either. The goddess Dione (in her name simply the "Goddess") is sometimes taken by later mythographers as a mere feminine form of Zeus (see entry Dodona): if this were so, she would not have assembled here.
The Lycian Peasants
According to Ovid's Metamorphoses, when Leto was wandering the earth after giving birth to Apollo and Artemis, she attempted to drink water from a pond in Lycia. The peasants there refused to allow her to do so by stirring the mud at the bottom of the pond. Leto turned them into frogs for their inhospitality, doomed to forever swim in the murky waters of ponds and rivers. This scene is represented in the central fountain in the parc of Versailles.