It comprises the four islands of the western part of the Pontine archipelago in the Gulf of Gaeta (central Tyrrhenian Sea): Ponza itself, Palmarola, Zannone, and Gavi.

The main centre of the island is the port of Ponza, which stands towards the southern end of the eastern coast and is the seat of the commune.

Other settlements include Guarini, Giancos, I Conti and Santa Maria in the centre of the island and Campo Inglese and Le Forna in the north.

The church of San Silverio recalls Pope Silverius’ death while in exile on the island.

The island of Zannone is some 10 kilometres (6 mi) to the north-east of Ponza and is completely uninhabited: even overnight stays are prohibited.