Squeezed between Attica and the Peloponnese, Aegina figured out very early that geography is destiny. The island's roughly triangular shape — dominated by an extinct volcano and ringed by stony but fertile plains — made it a natural waypoint for Aegean trade. By the 7th century BC, Aeginetan merchants were among the three principal players at the emporium of Naucratis in Egypt. They helped pioneer a standard of weights and measures that rivaled the Euboic-Attic system across the entire Greek world. When Persia threatened, Aegina initially hedged its bets — submitting symbolically to Achaemenid Persian heralds in 491 BC in a move Athens branded as treason. But when Xerxes' fleet finally arrived, Aegina's naval contingent fought at the Battle of Salamis in 480 BC with such distinction that the prize of valor was awarded to Aegina, not Athens. Herodotus, writing in the Athenian tradition, probably understated their role. The truth, scholars believe, is that the destruction of the Persian fleet was as much the Aeginetans' achievement as the Athenians'.

Aegina's history is a succession of rulers who came by sea. The Macedonians, Achaeans, Aetolians, and Romans each left their mark. The Venetians held the island from 1451 until 1537, when the Ottoman admiral Hayreddin Barbarossa invaded in October of that year. He captured Paliachora — the Byzantine-era hilltop settlement that served as the island's main town — on the fourth day, spared the Latin church of St. George, and then had the adult male population massacred. Six thousand surviving women and children were taken away as enslaved people. The island was left nearly empty. It was repopulated in 1579 by Greeks from the mainland and a small number of Albanians, who gradually assimilated. Centuries of struggle followed. Then came an unlikely transformation: in 1896, a physician named Nikolaos Peroglou introduced pistachio cultivation to the island. By 1950, pistachios had displaced almost every other crop, thanks to the island's volcanic soil and dry climate — conditions that produce a nut of exceptional quality. Today, "Fistiki Aeginis" holds a Protected Designation of Origin status, granted in 1996, and the annual Fistiki Fest each September draws visitors from across Greece.

After centuries of Ottoman rule, the Greek War of Independence brought Aegina an unexpected moment of national significance. Ioannis Kapodistrias, the first governor of free modern Greece, established his administration here in 1828. The Tower of Markellos — probably built during the second Venetian occupation as a watchtower — became the headquarters of the embryonic Greek state from 1826 to 1828. Kapodistrias also constructed the building now known locally, with dark irony, as "The Prison": the Orphanage of Kapodistrias, built in 1828–29 to house children orphaned by the war. At various times it held the National Public Library, the National Archaeological Museum, a military academy, the National Printing Office, and the National Conservatory. From about 1880 it was used as a prison, including for political prisoners during the Greek military junta of 1967–1974. Plans to restore it as a museum remain ongoing. A statue of Kapodistrias in the town's main square still watches over the port.

Two monuments define Aegina's ancient landscape. The Temple of Aphaea, built around 490 BC on a pine-clad hill in the island's northeast, is considered one of the best-preserved Doric temples in Greece. It formed part of a sacred triangle with the Athenian Parthenon and the Temple of Poseidon at Sounion — an equilateral arrangement of holy sites spanning the Saronic Gulf. The single standing column at Colona, the island's ancient acropolis north of the main town, marks the sanctuary of Apollo: Venetian sailors used its columns as navigational landmarks, giving the site its modern name. Further inland, the ghost settlement of Paliachora — sometimes called "the Mystras of Aegina" — preserves more than 35 Byzantine and Venetian-era churches on a ruined hillside, many still decorated with faded wall paintings from the 17th and 18th centuries. It was the island's capital from the Byzantine period until Barbarossa's raiders drove the population away for good in 1537.

Aegina's name comes from a figure in Greek mythology: Aegina, daughter of the river god Asopus, was abducted by Zeus and brought to this island, where she gave birth to Aeacus, who became its king. The island was also, legend held, where Zeus created the Myrmidons — an elite warrior race fashioned from ants — who later fought under Achilles at Troy. Myth and fact are woven together here in ways that are hard to separate. The island's Famous Aeginetans list runs from mythological heroes to Saint Nectarios of Aegina (1846–1920), whose monastery draws pilgrims today, to the American novelist Gustav Hasford, who wrote the book behind the film Full Metal Jacket, moved to Aegina, and died there of heart failure in 1993. The island has always attracted people looking for something the mainland couldn't give them.