Penteli Monastery, Orthodox monastery in Penteli Municipality, Greece.

Penteli Monastery is a stone and whitewashed complex on Mount Penteli's southern slope, roofed in red terracotta tiles. Two long two-storey wings with arched upper openings meet at a right angle around a paved courtyard, where a small red-domed church with apses stands beside a white stone bell tower. High walls and heavy doors give it a fortress-like appearance.

Saint Timotheos of Euripos, an Attica-born bishop who had fled Turkish persecution, founded the monastery in 1578; the monks built it where they found an ascetic's bones and a small icon of the Virgin. Part of the Katholikon, the south side and the fortified gate tower went up under his rule, and by 1650 the main building was finished, the Katholikon with a narthex and frescoes. It was destroyed after the Venetian occupation of Athens in 1688–1690 and again during the Greek War of Independence.

The monastery celebrates the Dormition of the Theotokos on 15 August and its founder, Saint Timotheos, on 16 August, as well as the Monday of the feast of the Holy Spirit. Its Katholikon, in post-Byzantine style, received a narthex and fresco decoration by 1650. The complex also holds a museum and a library.

The monastery is open to visitors during daylight hours but requires modest dress as a sign of respect for the sacred site. It helps to check ahead for specific visiting times and wear comfortable shoes, as the complex sits on a mountain slope.

During the 1778 Athens plague outbreak, this monastery served as a refuge for local residents seeking escape from the disease. This gave it an important role in the community's history during a time of great crisis.