According to the Bibliotheca of pseudo-Apollodorus, Atalanta was the daughter of Iasus, son of Lycurgus, and Clymene, daughter of Minyas. She is also mentioned as the daughter of Mainalos or Schoeneus, according to (Hyginus), of a Boeotian (according to Hesiod), or of an Arcadian princess (according to the Bibliotheca). The Bibliotheca is the only source which gives an account of Atalanta’s birth and upbringing. King Iasus wanted a son; when Atalanta was born, he left her on a mountaintop to die. Some stories say that a she-bear suckled and cared for Atalanta until hunters found and raised her, and she learned to fight and hunt as a bear would. She was later reunited with her father.
When Artemis was forgotten at a sacrifice by King Oineus, she was angered and sent the Calydonian Boar, a wild boar that ravaged the land, men, and cattle and prevented crops from being sown. Atalanta joined Meleager and many other famous heroes on a hunt for the boar. Many of the men were angry that a woman was joining them, but Meleager, though married, lusted for Atalanta, and so he persuaded them to include her. Several of the men were killed before Atalanta became the first to hit the boar and draw blood. After Meleager finally killed the boar with his spear, he awarded the hide to Atalanta. Meleager’s uncles, Plexippus and Toxeus, were angry and tried to take the skin from her. In revenge, Meleager killed his uncles. Wild with grief, Meleager's mother Althaea threw a charmed log on the fire, which consumed Meleager's life as it burned.
After the Calydonian boar hunt, Atalanta was rediscovered by her father. He wanted her to be married, but Atalanta, uninterested in marriage, agreed to marry only if her suitors could outrun her in a footrace. Those who lost would be killed. King Schoeneus agreed, and many young men died in the attempt until Hippomenes came along. Hippomenes asked the goddess Aphrodite for help, and she gave him three golden apples in order to slow Atalanta down. The apples were irresistible, so every time Atalanta got ahead of Hippomenes, he rolled an apple ahead of her, and she would run after it. In this way, Hippomenes won the footrace and came to marry Atalanta. Eventually they had a son Parthenopaios, who was one of the Seven against Thebes. Zeus or his mother Rhea turned Atalanta and Hippomenes into lions after they made love together in one of his temples. Other accounts say that Aphrodite changed them into lions because they did not give her proper honor. The belief at the time was that lions could not mate with their own species, only with leopards; thus Atalanta and Hippomenes would never be able to remain with one another.
In many versions of the quest for the Golden Fleece, for instance that published by Robert Graves in 1944, Atalanta sailed with the Argonauts as the only woman among them. She jumped aboard the ship soon after the expedition set out, invoking the protection of Artemis, whose virgin priestess she was. She was following Meleager, who had put away his young wife for Atalanta's sake. Atalanta returned his love but was prevented by an oracle from consummating their union, being warned that losing her virginity would prove disastrous for her. In disappointment Meleager joined the Argo, but Atalanta would not let him out of her sight. She plays a major part in various adventures of Jason's crew, suffered injury in a battle at Colchis, and was healed by Medea. Apollonius of Rhodes, on the other hand, claims Jason would not allow a woman on the ship because she would cause strife on the otherwise all-male expedition (Argonautica 1.769–73).