Which river god fought against Achilles?

Scamander was the river god who fought against Achilles in the Iliad.

Scamander personifies the river flowing across the Trojan plain, where much of the war's fighting takes place. Homer also calls him Xanthus: “Scamander” is the name used by mortals, while “Xanthus” is associated with the gods. The river's location made it central to the battle around Troy.

After Achilles kills large numbers of Trojans and clogs the river with corpses, Scamander angrily confronts him. The river god tries to overwhelm the Greek hero with surging water and nearly drowns him. Achilles is saved when Hera and Athena call on Hephaestus, whose firestorm forces Scamander back and dries his waters.

Simoeis is an easy source of confusion because it was another river god of the Trojan plain and supported Scamander. However, Simoeis does not take the principal direct role in the fight. Alpheus and Cephissus are river gods connected with other Greek regions and myths.