Artemis was one of the most widely venerated of the Ancient Greek deities and one of the oldest. In the classical period of Greek mythology, Artemis (Greek: (nominative) Ἄρτεμις, (genitive) Ἀρτέμιδος) was often described as the daughter of Zeus and Leto, and the twin sister of Apollo. She was the Hellenic goddess of forests and hills, child birth, virginity, fertility, the hunt, and often was depicted as a huntress carrying a bow and arrows. The deer and the cypress were sacred to her. In later Hellenistic times, she even assumed the ancient role of Eileithyia in aiding childbirth.
Artemis later became identified with Selene, a Titaness who was a Greek moon goddess, sometimes depicted with a crescent moon above her head. She was also identified with the Roman goddess Diana, with the Etruscan goddess Artume, and with the Greek or Carian goddess Hecate.
Various conflicting accounts are given in Classical Greek mythology of the birth of Artemis and her twin brother, Apollo. All accounts agree, however, that she was the daughter of Zeus and Leto and that she was the twin sister of Apollo.
An account by Callimachus has it that Hera forbade Leto to give birth on either terra firma (the mainland) or on an island. Hera was angry with Zeus, her husband, because he had impregnated Leto. But the island of Delos (or Ortygia in the Homeric Hymn to Artemis) disobeyed Hera, and Leto gave birth there.
A scholium of Servius on Aeneid iii. 72 accounts for the island's archaic name Ortygia  by asserting that Zeus transformed Leto into a quail (ortux) in order to prevent Hera from finding out his infidelity, and Kenneth McLeish suggested further that in quail form Leto would have given birth with as few birth-pains as a mother quail suffers when it lays an egg.
The myths also differ as to whether Artemis was born first, or Apollo.
The childhood of Artemis is not embodied in any surviving myth: the Iliad reduced the figure of the dread goddess, making her a girl, who, having been thrashed by Hera, climbs weeping into the lap of Zeus. A poem of Callimachus – the goddess "who amuses herself on mountains with archery" – imagines some charming vignettes: at three years old, Artemis asked her father, Zeus, while sitting on his knee, to grant her six wishes. Her first wish was to remain chaste for eternity, and never to be confined by marriage. She then asked for lop-eared hounds, stags to lead her chariot, and nymphs to be her hunting companions, 60 from the river and 20 from the ocean. Also, she asked for a silver bow like her brother Apollo. He granted her the six wishes. All of her companions remained virgins and Artemis guarded her own chastity closely. Her symbol was the silver bow and arrow.
Artemis, the goddess of forests and hills, was worshipped throughout ancient Greece.. Her best known cults were on the island of Delos (her birthplace); in Attica at Brauron and Mounikhia (near Piraeus); in Sparta. She was often depicted in paintings and statues in a forest setting, carrying a bow and arrows, and accompanied by a deer.
As Aeginaea, she was worshiped in Sparta; the name means either huntress of chamois, or the wielder of the javelin (αιγανέα). She was worshipped at Naupactus as Aetole; in her temple in that town there was a statue of white marble representing her throwing a javelin. This "Aetolian Artemis" would not have been introduced at Naupactus, anciently a place of Ozolian Locris, until it was awarded to the Aetolians by Philip II of Macedon. Strabo records another precinct of "Aetolian Artemos" at the head of the Adriatic. As Agoraea she was the protector of the agora. As Agrotera, she was especially associated as the patron goddess of hunters. In Elis she was worshiped as Alphaea. In Athens Artemis was often associated with the local Aeginian goddess, Aphaea. As Potnia Theron, she was the patron of wild animals; Homer used this title. As Kourotrophos, she was the nurse of youths. As Locheia, she was the goddess of childbirth and midwives. She was sometimes known as Cynthia, from her birthplace on Mount Cynthus on Delos, or Amarynthia from a festival in her honor originally held at Amarynthus in Euboea. She was sometimes identified by the name Phoebe, the feminine form of her brother Apollo's solar epithet Phoebus.
The ancient Spartans used to sacrifice to her as one of their patron goddesses before starting a new military campaign.
Pre-pubescent Athenian girls and young Athenian girls approaching marriageable age were sent to the sanctuary of Artemis at Brauron to serve the Goddess for one year. During this time the girls were known as arktoi, or little she-bears. A myth explaining this servitude relates that a bear had formed the habit of regularly visiting the town of Brauron, and the people there fed it, so that over time the bear became tame. A young girl teased the bear, and, in some versions of the myth it killed her, while in other versions it clawed her eyes out. Either way, the girl's brothers killed the bear, and Artemis was enraged. She demanded that young girls "act the bear" at her sanctuary in atonement for the bear's death.
Virginal Artemis was worshipped as a fertility/childbirth goddess in some places, assimilating Ilithyia, since, according to some myths, she assisted her mother in the delivery of her twin. During the Classical period in Athens, she was identified with Hecate. Artemis also assimilated Caryatis (Carya).