In Greek mythology Acheron was one of the five rivers of the underworld; the river of woe that encircled Hades’ domain.

In theory Acheron was a Potamoi, a river god, and therefore the offspring of Oceanus and Tethys. Each river of ancient Greece had a god associated with it, just as every spring had a Naiad, and every stream and rain cloud an Oceanide.

A specific myth though did spring up to explain the particular existence of the Acheron. Stories state how Acheron was once the son of Helios (sun) and Gaia (earth); during the Titanomachy Acheron supported the Titans against Zeus and his siblings by providing refreshment to the Titans. The Olympian gods were eventually victorious in the war, and as punishment for aiding the enemy Acheron was turned into the underworld river.

In any event the river Acheron became, in mythology, one of the five rivers of Hades; alongside the rivers Styx, Lethe, Cocytus and Phlegethon.

In many ways it could be considered the most important of the rivers, as despite the confused nature of the geography of the underworld, the Acheron is considered the first river faced by the deceased.

To get into the underworld, and to be subsequently judged, the departed needed to be ferried across the river by Charon, the daemon ferryman. To pay Charon the deceased should have been buried with an obolus in their mouth; as those unable to pay would wander along the banks of the Acheron for a hundred years. Some myths do suggest that those by the banks would wander until they find the hidden paupers entrance.

Once the deceased found themselves upon the far banks of the Acheron, they would be faced with the mighty three headed dog, Cerberus. Cerberus guarded the gates to Hades, and whilst he would let all enter, no one was allowed to subsequently leave.

With the Acheron prominently placed in the underworld it is only naturally that the river would appear in mythological tales involving Theseus, Odysseus, Heracles and Aeneas, as the heroes entered and departed from the underworld, despite the guarding of Cerberus.

The oldest Greek sources, when talking about the geography of Hades, did tend to have the Phlegethon and Cocytus flowing into the Acheron, whilst later Roman writers had the Cocytus and Styx flowing from it. It also later Roman writers who started associated the mythology of Charon and Cerberus with the River Styx.