Tyrrhenian Sea (tĭrēˈnēən) [key], Ital. Tirreno, part of the Mediterranean Sea, c.475 mi (760 km) long and from 60 to 300 mi (97–483 km) wide, between the Ligurian Sea, the Italian peninsula, Sicily, Sardinia, and Corsica. The Strait of Messina connects it with the Ionian Sea. The sea is named for the Tyrrhenoi (an ancient name for the Etruscans). Naples and Palermo are the chief ports.