Ancient Neolithic and Bronze Age settlement sites have been found in the Santa Marinella area. From the 9th century B.C., the settlement of Punicum, the settlement of Pyrgi (present-day Santa Severa), a likely Phoenician emporia, and finally the Roman settlement of Castrum Novum appeared in the area.
In the Middle Ages, the Santa Marinella coastline fell into the possession of the Lords of Vico, then the Anguillara and finally the Orsini.
Among the coastal defence towers built by Pope Pius V in 1567, there is the tower that was named Santa Marinella, after the small village that had risen there for the cultivation of fields and pastures.
According to tradition, around the year 1000 a community of Basilian monks from the Middle East, after arriving in southern Italy, sailed up the Tyrrhenian Sea and settled on the promontory where the Odescalchi Castlestands today. They built the village, the monastery and a small adjoining church dedicated to Saint Marina and Saint Leonard, thus introducing the cult of the saint.
The small church, which has now disappeared, may have been incorporated into the Odescalchi castle as a palace chapel around the 16th century, in order to build the future parish church on the site.
In 1435, Pope Eugene IV granted the Santa Marinella estate to the canons of Santo Spirito in Sassia.