In Greek mythology, Calydon was founded by Aetolus — the same mythical ancestor from whom the region takes its name — on land previously held by the Curetes tribe. Aetolus named the city after his son Calydon. From the beginning, the Calydonians and the Curetes were in conflict, and the Iliad preserves a vivid account of one of their battles.

But it is the Calydonian Boar hunt that gave the city its lasting fame. When King Oeneus of Calydon failed to honor Artemis in his harvest sacrifices, the goddess sent a monstrous boar to ravage the fields. Oeneus's son Meleager assembled a gathering of heroes to hunt it — among them Atalanta, Theseus, Jason, and Castor and Pollux. Meleager killed the beast, but the aftermath brought tragedy: disputes over the boar's hide led to a conflict with the Curetes, Meleager killed two of his mother's brothers in the fighting, and his mother burned the fateful brand on which his life depended. Meleager died. The myth, in its different versions, turns on questions of honor, family loyalty, and divine punishment — themes that made Calydon's story compelling enough for Homer to tell it in the Iliad.

In the historical period, Calydon changed hands repeatedly. By 391 BC it was in the possession of the Achaeans — the exact circumstances unclear, though it likely passed to those Achaeans who had been settled at nearby Naupactus after the Peloponnesian War. Pressed hard by the Acarnanians, the Achaeans at Calydon called on Spartan help, and Agesilaus II led an army into Aetolia. The city remained in Achaean hands until the Battle of Leuctra in 371 BC ended Spartan supremacy; Epaminondas then restored Calydon to the Aetolians.

Calydon's location on the west bank of the Evenus River, about 11 kilometers from the sea, gave it access to trade routes without full coastal exposure. It remained significant enough that Julius Caesar and Pompey's forces were still treating it as a meaningful place during their civil war in 48 BC. A few years later, that significance ended. Augustus founded Nicopolis to commemorate his victory at the Battle of Actium in 31 BC, and obliged the inhabitants of Calydon to relocate. The city was not destroyed so much as drained — of people, purpose, and eventually its most sacred possessions.

Calydon was the center of the cult of Artemis Laphria — a particular aspect of Artemis associated with wilderness and the spoils of the hunt, the "Laphrios" aspect that the Aetolians revered throughout their region. The goddess had a sanctuary at Calydon, and her cult statue was one of the city's most prized objects.

When Augustus depopulated Calydon to fill Nicopolis, he gave the statue of Artemis Laphria to Patrae in Achaea. A statue of Dionysus that had stood at Calydon was also moved to Patrae. Near the city, Apollo had a temple — Apollo Laphrius — and there was a lake known for its fish. The cult of Artemis was not merely relocated; it was redistributed as a political gift, the goddess becoming an instrument of imperial city-building. The Calydonian Boar hunt, which had once drawn the heroes of the Greek world to this plain, was now a myth belonging to a depopulated ruin.

The site of ancient Calydon lies north of the modern village of Evinochori in the Aetolia-Acarnania regional unit. Archaeological excavations have uncovered a Hellenistic theatre of an unusual square plan — most ancient theatres followed a roughly semicircular form, making the square plan at Calydon a distinctive architectural choice. A Hellenistic Heroon, used as a wrestling ground, contained a rich tomb underneath its floor. The sanctuary of Artemis Laphria revealed a temple of Artemis and a smaller temple of Apollo, along with remains of other structures spanning the Geometric to Hellenistic periods — evidence of continuous use of the sacred site across many centuries.

Lower down, excavations uncovered a peristyle house and kilns in what was once the lower town, and a house from the 2nd century BC on the lower acropolis. Finds from the site — terracottas from the temple of Artemis and much else — are displayed in the Archaeological Museum of Agrinion and in the National Archaeological Museum in Athens. Above the ruins, a modern infrastructure coincidence: one of the tunnels of the A5 motorway passes beneath the site, and is named the Calydon Tunnel in honor of the city whose ground it crosses.