Alebion was a demigod and a son of Poseidon.
Alebion was a son of Poseidon and was the brother of Bergion who attacked Heracles with Dercynus when he passed through their country, Liguria in North-Western Italy, on his way back to Mycenae from Iberia having obtained the cattle of Geryon as his tenth labour. The battle that followed was fierce; Albion and Dercynus or Bergion were supported by a numerous army.
Hercules and his army were in a difficult position so he prayed to his father Zeus for help. With the Aegis of Zeus, Heracles won the battle and both brothers were killed. It was this kneeling position of Heracles when prayed to his father Zeus that gave the name Engonasin, meaning "on his knees" or "the Kneeler" to Heracles' constellation.