The Aktio–Preveza Undersea Tunnel is an undersea road tunnel across the mouth of the Ambracian Gulf in western Greece. It links Epirus and the city of Preveza on the north shore of the gulf with the cape of Aktio (Actium) in Aetolia-Acarnania, in Central Greece. Completed in 2002, the tunnel is an important piece of infrastructure in a previously underdeveloped region, and greatly shortens the travel distance between the two sides of the gulf, which previously was only possible by ferry. It is the first and so far only undersea tunnel in Greece.