Ionia () is a former municipality on the island of Chios, North Aegean, Greece. Since the 2011 local government reform it is part of the municipality Chios, of which it is a municipal unit. It is located in the southeastern part of the island, and has a land area of 48.272 km². Its population was 4,650 at the 2001 census. The seat of the municipality was in Kallimasia (pop 930). Its largest town is Nénita (1,038). Other large towns are Tholopotámi (761) and Katarráktis (425).