Santa Marinella is a comune (municipality) in the Metropolitan City of Rome Capital, in the Italian region of Lazio, located about 60 kilometres (37 mi) northwest of Rome.

It includes the beach resort of Santa Severa (the ancient Pyrgi), and a medieval castle.

In antiquity, Santa Marinella was the site of Punicum, an important Etruscan port which served the city of Caere. Punicum was identified in the Peutinger Table, in which it is on the Via Aurelia 9km N of Pyrgi. The area had several scattered settlements in Etruscan times. It was near an easy landing point, protected from the winds and the sea. The name Punicum is probably from the Latin name of the pomegranate (malum punicum) a plant which in ancient times was often used as a topographical reference point (ad punicum).

There was a Sanctuary of Minerva overlooking the Punto della Vipera north of S. Marinella, finds from which are in the museum.

In the suburbs to the north of Cape Linaro was the Roman town of Castrum Novum of which parts are visible in the sea and others have been recently excavated.

About 10km northeast are the remains of the baths of Aquae Caeretanae famous until the 5th century.

It became a Roman resort and site of many opulent villas under the Empire.

Numerous Roman bridges are preserved of the ancient Via Aurelia, the famous road linking Rome, coastal Etruria and Liguria, built from the 3rd century BC based on earlier Etruscan layouts.