The son of Heracles and Psophis. Promachus and his twin brother Echephron were brought up by Heracles' friend Lycortas in Phegia, a city called Erymanthus before the reign of Phegeus. They later changed the name of Phegia to Psophis, the name of their mother.
- Pausanias. Description of Greece viii, 24.2.