It is connected to the Adriatic Sea to the north, and is bounded by Southern Italy, including Basilicata, Calabria, Sicily, and the Salento peninsula to the west, southern Albania (and western Apulia, Italy) to the north, and the west coast of Greece, including the Peloponnese.

They are collectively named the Ionian Islands, the main ones being Corfu, Kefalonia, Zakynthos, Lefkada, and Ithaca.

There are ferry routes between Patras and Igoumenitsa, Greece, and Brindisi and Ancona, Italy, that cross the east and north of the Ionian Sea, and from Piraeus westward.

[9] When Dyrrhachus was attacked by his own brothers, Heracles, who was passing through the area, came to his aid, but in the fight the hero killed his ally's son by mistake.

[10] The International Hydrographic Organization defines the limits of the Ionian Sea as follows:[11] From south to north in the west, then north to south in the east: The Ionian Sea was regularly crossed since at least the 8th century BC, by ancient Greek colonizers who were establishing colonies in Italy.