The river Eridanos /əˈrɪdəˌnɒs/ or Eridanus (/əˈrɪdənəs/; Ancient Greek: Ἠριδανός, "Amber") is a river mentioned in Greek mythology. Virgil considered it one of the rivers of Hades in his Aeneid VI, 659.
Hesiod, in the Theogony, calls it "deep-eddying Eridanos" in his list of rivers, the offspring of Tethys. Herodotus (III, 115) points out that the word Eridanos is essentially Greek in character, and surmises that consequently the river supposed to run around the world is probably a Greek invention. He associated it with the river Po, because the Po was located near the end of the Amber Trail. According to Apollonius of Rhodes and Ovid,amber originated from the tears of the Heliades, encased in poplars as dryads, shed when their brother, Phaeton, died and fell from the sky, struck by Zeus' thunderbolt, and tumbled into the Eridanos, where "to this very day the marsh exhales a heavy vapour which rises from his smouldering wound; no bird can stretch out its fragile wings to fly over that water, but in mid-flight it falls dead in the flames;" "along the green banks of the river Eridanos," Cygnus mourned him—Ovid told—and was transformed into a swan. There in the far west, Heracles asked the river nymphs of Eridanos to help him locate the Garden of the Hesperides.