The Fourth Shore (Italian: Quarta Sponda) was the name created by Benito Mussolini to refer to the Mediterranean shore of coastal Libya (then an Italian colony) and World War II Italian Tunisia in the fascist-era Kingdom of Italy, during the late Italian Colonial Empire period of Libya and the Maghreb.
The term "Fourth Shore" derives from the geography of Italy being a long and narrow peninsula jutting into the Mediterranean Sea with two principal shorelines: the First Shore on the east along the Adriatic Sea and the Second Shore on the west along the Tyrrhenian Sea. The Adriatic Sea's opposite western Balkans shore, with Dalmatia, Montenegro, and Albania, was planned for Italian expansion as the Third Shore, with Libya on the Mediterranean becoming the fourth. Thus the Fourth Shore was the southern part of Greater Italy, an early 1940s Fascist project of enlarging Italy's national borders around Italy's Mare Nostrum.
After the Italian Empire conquest of Ottoman Libya in the 1911–1912 Italo-Turkish War, much of the early colonial period had Italy waging a war of subjugation against Libya's population. Ottoman Turkey surrendered its control of Libya in the 1912 Treaty of Lausanne, but fierce resistance to the Italians continued from the Senussi political-religious order, a strongly nationalistic group of Sunni Muslims. This group, first under the leadership of Omar Al Mukhtar and centered in the Jebel Akhdar Mountains of Cyrenaica, lead the Libyan resistance movement against Italian settlement in Libya. Italian forces under the Generals Pietro Badoglio and Rodolfo Graziani waged punitive pacification campaigns which turned into brutal and bloody acts of repression, even as a consequence of many killings of Italian soldiers and prisoners of war since 1911. Resistance leaders were executed or escaped into exile. The forced migration of more than 100,000 Cyrenaican people ended in Italian concentration camps. After two decades Italy predominated.