In Greek mythology, Alpheus (Alpheios) is the river-god of the Peloponnesian Alpheios, child of Oceanus and Tethys. He is best known for pursuing the nymph Arethusa to Ortygia at Syracuse, where their waters were said to mingle under the sea. He also figures in the labour of the Augean stables and in local Elian cult shared with Artemis.
Adapted from Wikipedia, "Alpheus (deity)" · CC BY-SA 4.0
I.Arethusa and Artemis
Pausanias and Ovid tell how Alpheus hunted or surprised Arethusa; she fled to Ortygia and became a spring, while the river pursued beneath the sea to unite with her. A cup cast into the Alpheios was popularly said to surface in Arethusa's well—an aition for Syracuse's famous fountain.
Other Elian tales make Artemis herself the object of his love: she and her nymphs smear their faces with mud at Letrini so he cannot tell them apart, whence a temple of Artemis Alphaea; at Olympia the two divinities shared an altar.
II.Offspring and the Augean labour
Through Telegone he was father of Orsilochus and ancestor of Homeric warriors; other notices give him daughters such as Melantheia. A separate pseudo-Plutarchian tale makes him a son of Helios who leaps into a river after killing his brother.
In Heracles' fifth labour the hero diverts the Alpheios (with the Peneius) to wash out the Augean stables in a day. Syracusan coinage under Gelon already used Alpheus' head to evoke the city's foundation myth tied to Arethusa.