Torre di San Gemiliano, Coastal watchtower in Arbatax, Italy.

The Torre di San Gemiliano is a truncated-cone watchtower on Sardinia's eastern coast in Ogliastra, a few hundred metres from Arbatax and about four kilometres from Tortolì. It stands 12 metres high with a diameter of only 7 metres, giving it a slender profile, and holds a single room of about 13 square metres inside.

The tower dates to the early 17th century, when it was built as a lookout and immediate defence against pirate attacks. It formed part of the coastal defence, surveillance and communication system that guarded Sardinia's coast from the early Middle Ages until the mid-19th century. It kept visual contact with the tower of Barì and with the no-longer-existing tower of Bellavista.

The tower represents the strategic defense network of Sardinia, connected visually with towers of Barì and Bellavista for coastal surveillance.

The tower can be reached on foot from the beach or along an unpaved lane that meets Via San Gemiliano. The structure is open to visitors, and the climb leads to a viewpoint over the beaches of Orrì and Cea.

The tower stands 42 metres above sea level and its sightline reached 25 kilometres out to sea, linking it visually with the Torre di Barì and the now-vanished Torre di Bellavista. From the top, the beaches of Orrì and Cea come into view.