ARETHUSA, a fountain at Syracuse, in Sicily, famed among the ancients for the abundance of its waters and the number of its fishes, but still more so for the connection which was fabled to exist between it and Alpheus, the river of the Peloponnesus, “who stole under seas to meet his Arethuse.” According to the anthropomorphic legend, Arethusa was a daughter of Nereus and Doris, who was changed into the fountain by her mistress Diana (Artemis), to deliver her from the pursuit of her lover Alpheus. There is still a copious supply of water in the modern fountain, but the taste is brackish, and it can only be used for washing; while the fish are no longer to be found. There was a fountain of the same name in Ithaca (Homer), and another at Chalcis in Euboea, which supplied the city with water, but, according to Leake, has now disappeared. There was also a lake Arethusa, through which the Tigris flowed, identified by Ritter with L. Nazuk.

Arethusa was also the name of two cities: Arethusa in Macedonia, famous for the tomb of Euripides, and Arethusa in Syria (Rastan), which gives its name to Marcus, a bishop who was persecuted by the Arethusans, and is honoured as a martyr by the Greek Church.