What is the name of the river of boiling blood in the seventh circle?

The river of boiling blood in Dante’s seventh circle is called Phlegethon. It forms part of the punishment for violent sinners, especially those who committed violence against other people.

Dante’s Phlegethon is a blood-red river boiling with extreme heat. The violent are submerged to different depths according to the seriousness of their crimes. Centaurs patrol the banks and shoot arrows at anyone who tries to rise above the assigned level. The centaur Chiron leads Dante and Virgil across the river on Nessus’s back.

The name comes from Greek mythology. Phlegethon, whose name is associated with burning or fiery flow, is one of the rivers of the Underworld described in ancient tradition. Dante reshapes that classical river into a specifically moral landscape, making the liquid itself resemble the blood shed by the violent.

Phlegethon is easy to confuse with Acheron, Styx, and Lethe, which are other famous Underworld rivers. In Dante’s poem, Acheron marks the entrance to Hell, Styx contains the wrathful, and Lethe appears in Paradise after the earthly paradise—not as the seventh circle’s boiling river.