The names of the rivers in Hades, the underworld of Greek mythology, are Acheron, Cocytus, Lethe, Phlegethon and Styx. The Styx is the most widely known of these five rivers.
The name "Styx" comes from the Greek word "stygos," meaning "hatred." The other rivers also reflect emotions or experiences associated with death. The Acheron was the river of woe, the Lethe was the river of oblivion and forgetfulness, the Phlegethon was the river of fire and the Cocytus was the river of cries of lamentation. To access the underworld, dead souls had to cross either the Styx or the Acheron. The Phlegethon led deep into Tartarus, the chambers of torture and suffering into which particularly bad souls were condemned.