In Greek mythology, Arethusa (/ˌærɪˈθjuːzə/; Ancient Greek: Ἀρέθουσα, romanized: Aréthousa) is a minor figure who became a lover of the sea-god Poseidon, before undergoing a transformation at the hands of Hera during a lost episode of Greek myth. She then became the spring of the same name in Chalcis.
The New Archaeological Museum of Chalcis was named 'Arethusa' after this legendary woman.