The Peloponnese became an island when the Corinth Canal opened in 1893.
The Peloponnese is a large peninsula in southern Greece, connected to mainland Greece by the narrow Isthmus of Corinth. Excavation of the Corinth Canal cut through the isthmus and created a navigable waterway linking the Gulf of Corinth with the Saronic Gulf.
Although technically an island after the canal’s completion, the Peloponnese is commonly still called a peninsula because the canal is artificial and the region has a long-standing geographic identity as southern Greece. The name means “island of Pelops,” referring to the mythological hero Pelops.
The peninsula contains important ancient sites including Olympia, Mycenae, Epidaurus and Corinth. Modern administrative geography treats it as a Greek peninsula and regional area, while the separate island of Euboea lies farther east and is not part of the Peloponnese.