The
Gulf of Euboea,
Euboean Gulf,
Euboic Sea or
Euboic Gulf (modern Greek: Ευβοϊκός Κόλπος,
Evvoïkós Kólpos) is an arm of the
Aegean Sea between the island of
Euboea (northeast coastline) and the Greek mainland (southwest coastline). Trending diagonally northwest-southeast, the gulf is divided by the narrow
Strait of Euripus, at the town of
Chalcis (Khalkís). The
North Euboean Gulf is about 50 miles (80 km) long and up to 15 miles (24 km) wide, and the
South Euboean Gulf is about 30 miles (48 km) long, with a maximum width of 9 miles (14 km).