Which river in the underworld causes forgetfulness when drunk? Lethe is the river whose water erases memory. In Greek mythology, Lethe flows through Hades, and the dead who drink from it lose remembrance of their former lives. Its name comes from the ancient Greek word for forgetting or concealment.
Lethe is traditionally counted among the five rivers of the underworld. The others are usually Acheron, associated with sorrow; Cocytus, the river of lamentation; Phlegethon, the river of fire; and Styx, the boundary river whose waters also carry powerful divine significance. These roles overlap in later retellings, which can make underworld geography seem more fixed than it really was.
The idea became especially important in stories about reincarnation. In Plato’s Myth of Er, souls approach the plain of Lethe and drink from the river Ameles, or “careless” river, before returning to life. Orphic traditions instead describe a pool of Mnemosyne, memory, whose waters initiates were encouraged to choose so they could retain knowledge after death.
Lethe also influenced later literature. Dante uses it in Purgatorio as a river that removes the memory of sin, while Shakespeare invokes its forgetful waters in Hamlet. Lethe is therefore more than a place-name: it represents oblivion, rebirth, and the tension between forgetting and remembering.