Aegina (; Ancient Greek: ) was a figure of Greek mythology, the nymph of the island that bears her name, Aegina, lying in the Saronic Gulf between Attica and the Peloponnesos. The archaic Temple of Aphaea, the "Invisible Goddess", on the island was later subsumed by the cult of Athena. Aphaia () may be read as an attribute of Aegina that provides an epithet, or as a doublet of the goddess.
Though the name Aegina betokens a goat-nymph, such as was Cretan Amalthea, she was given a mainland identity as the daughter of the river-god Asopus and the nymph Metope; of their twelve or twenty daughters, many were ravished by Apollo or Zeus. Aegina bore at least two children: Menoetius by Actor, and Aeacus by Zeus, both of whom became kings. A certain Damocrateia, who married Menoetius, was also called her daughter by an unknown consort.
The mortal son Menoetius was king of Opus, and was counted among the Argonauts. His son was Patroclus, Achilles' first cousin once removed through their paternal family connection to Aegina, and his intimate companion.
The son made immortal, Aeacus, was the king of Aegina, and was known to have contributed help to Poseidon and Apollo in building the walls of Troy. Through him Aegina was the great-grandmother of Achilles, who was son of Peleus, son of Aeacus.
It was often said that Zeus took the form of an eagle (or a great flame in Ovid's telling) and abducted Aegina, taking her to an island near Attica, then called Oenone; henceforth known by her name. Aegina's father Asopus chased after them; his search took him to Corinth, where Sisyphus was king. Sisyphus, having chanced to see a great bird bearing a maiden away to a nearby island, informed Asopus. Though Asopus pursued them, Zeus threw down his thunderbolts sending Asopus back to his own waters. Aegina eventually gave birth to her son Aeacus, who became king of the island.
When the city of Aegina was depopulated by a plague sent by Hera in jealous reprisal for Zeus's love of Aegina, the king Aeacus prayed to Zeus for the ants that were currently infesting an oak tree to morph into humans to repopulate his kingdom. Thus the myrmidons were created.