Inachus was the god of the river Inachus and a king of Argos. He was the son of Oceanus and Tethys, and he married his half-sister Melia, who bore him several children including Io.

His name is difficult to interpret with any obvious relevance: inodes means 'sinewy', 'fibrous' (this could have an erotic connotation), while einacis means 'nine times' (with possibly some ritual allusion). His name may even somehow link up with that of his daughter Io.