Icosium

Icosium is the ancient coastal city that stood on the Mediterranean near the site of present-day Algiers, the capital of Algeria. The city was originally established as a Phoenician trading post and subsequently came under Carthaginian influence, appearing in Greek and Latin sources under the name Icosium.

Under Roman rule, Icosium was incorporated into the province of Mauretania Caesariensis and developed as a significant port and urban center. It served as a hub for regional commerce and military movement in the western Mediterranean, and its ruins and inscriptions attest to its urban and economic activity during antiquity.

In late antiquity, Icosium remained inhabited and is known to have had a Christian community, including an episcopal see attested in the broader North African church sphere. The city’s fortunes declined in the face of changing imperial and regional dynamics as the Western Roman Empire dissolved and later powers controlled the area.

The Arab conquest of the Maghreb in the 7th century brought major population and cultural shifts. The name Icosium gradually disappeared from common use as the Arabic name al-Jazāʾir (the islands) began to be associated with the growing urban settlement that would become Algiers. Over time, the historical site of Icosium was subsumed by the development of the city that developed into modern Algiers.

Today, Icosium is studied as part of the ancient urban and maritime landscape of Roman North Africa, illustrating the region’s Phoenician, Punic, and Roman heritage and its enduring connection to the city of Algiers.