In Dante’s Purgatory, the river Lethe makes souls forget the memories of their sins. It flows through the Earthly Paradise at the summit of Mount Purgatory, where souls who have completed their purification are prepared to enter Heaven.
Dante is immersed in Lethe by Matelda, a mysterious woman who appears in the garden. Drinking or being washed in its waters removes the memory of sinful actions, symbolizing the soul’s complete cleansing after repentance and penance. Lethe is borrowed from classical mythology, where it is the river of forgetfulness in the underworld.
Lethe is paired with another river created and named by Dante: Eunoe. After drinking from Lethe, the soul drinks from Eunoe, which strengthens the memory of good deeds. The rivers therefore perform complementary tasks—Lethe erases the remembered burden of sin, while Eunoe restores and intensifies the memory of virtue. Styx belongs to the Inferno, not Purgatory.