The site where Cassis now sits was first occupied between 500 and 600 BC by the Ligures, who constructed a fortified habitation at the top of the Baou Redon. These people lived by fishing, hunting, and by farming.
The link with Massilia (Marseille), a city founded by the Phoceans,(Greek: Φώκαια), means that the current site of Cassis could have been inhabited by the Greeks, though no proof has yet been found.
During the Roman times, Cassis was part of the maritime route made by the Emperor Antoninus Pius. At this time, the port advanced right up to Baragnon. It was a small village, established mainly around the Arena and Corton beaches. The principal livelihood was fishing and maritime trade with North Africa and the Middle East. Several archaeological discoveries attest to this.
From the fifth to the tenth century, invasions by the barbarians led the population to seek refuge in the castrum, a fortified city that, in 1223, became the property of the Seigneurie des Les Baux-de-Provence.
In the fifteenth century, Cassis was ceded to the Counts of Provence, then René of Anjou gave the town to the Bishops of Marseille, who ruled the town until the Revolution of 1789
