Lynceus was a descendant of Belus through Aegyptus, twin brother of Danaus, who had fifty daughters, the Danaides, and Aegyptus had fifty sons (including Lynceus). Aegyptus commanded that his sons marry the Danaides and Danaus fled to Argos, ruled by King Pelasgus with his daughters. When Aegyptus and his sons arrived to take the Danaides, Danaus gave them to spare the Argives the pain of a battle. However, he instructed his daughters to kill their husbands on their wedding night. Forty-nine followed through, but one, Hypermnestra refused because her husband, Lynceus, honored her wish to remain a virgin. Danaus was angry with his disobedient daughter and threw her to the Argive courts. Aphrodite intervened and saved her. Lynceus later killed Danaus as revenge for the death of his brothers. Lynceus and Hypermnestra then began a dynasty of Argive kings (the Danaan Dynasty) beginning with Abas. In some versions of the legend, the Danaides were punished in the underworld by being forced to carry water through a jug with holes, or a sieve, so the water always leaked out.
Another Lynceus was the jealous murderer of Castor, along with his brother, Idas. Idas and Castor murdered Castor because they all (along with Polydeuces) sought Phoebe and Hilaeira, daughters of Leucippus (who was also Idas and Lynceus' uncle in some versions). Lynceus was one of the Argonauts and he participated in the hunt for the Calydonian Boar. He was a son of Aphareus and Arene and was said to have excellent sight, even able to see underground.