Sicyon (sĬsh´ēŏn, sĬs´–), ancient city of Greece, in the Peloponnesus, NW of Corinth and 2 mi (3.2 km) S of the Gulf of Corinth. Sicyon was founded by Argos and attained its greatest power under the tyrant Cleisthenes in the 6th cent. BC Under the leadership of the general Aratus, Sicyon joined (3d cent. BC) the Achaean League. With the destruction (146 BC) of Corinth by the Romans, Sicyon briefly regained power but subsequently declined. Sicyon was an important center of art. In the archaic period of Greek art (625–480 BC) it was famous for painting and pottery. In the 4th cent. BC the Sicyonic school of painting, founded by Eupompus, produced such artists as Pamphilus and Apelles.