Grotte de Saint-Michel-Archange, Cave church in Olevano sul Tusciano, Italy.

The Grotte de Saint-Michel-Archange is a cave sanctuary on the western slope of Monte Raione in Olevano sul Tusciano, about 600 m up in a cliff above the Tusciano valley. Inside, five separate buildings stand under the rock vault: a martyrion, a single-nave basilica with Lombard-era frescoes, two votive shrines with a courtyard, a church and an oratory, each with its own roof or dome.

The cave was already used by people during the Neolithic period and the Middle Bronze Age, long before it was transformed into a place of worship in the Middle Ages. This gradual religious conversion can still be read in the altars and frescoes cut into the rock.

The site's name comes from the Archangel Michael, to whom the cave was consecrated in the early centuries of Christianity, like the nearby sanctuary of Monte Sant'Angelo on the Gargano. From the decades 860–870 the sanctuary appears in written records, and it was later listed among the pilgrimage destinations on the routes to the Holy Land, alongside the tombs of the Apostles in Rome and Saint Michael on the Gargano.

Two trails lead to the cave, one from the Ariano hamlet and one from Salitto; they join shortly before the entrance, which is reached by a staircase. The walk from Ariano takes about an hour. The cave opens at roughly 600 m on the western slope of Monte Raione, above the Tusciano valley.

The sanctuary appears in the 1996 list of endangered monuments of the World Monuments Fund, and was excavated and restored in 2015 and 2016. Its buildings stand free inside the cave, with their own roofs and domes rather than using the natural vault as a ceiling.