Chiesa di San Giovanni ad insulam, Romanesque church in Isola del Gran Sasso d'Italia, Italy

San Giovanni ad Insulam is a Romanesque church built between the 11th and 13th centuries on a small hill above the Mavone River near Isola del Gran Sasso d'Italia. Its flat-ended facade, raised in the late 12th century, carries a horizontal cornice of alternating pointed and round arches on corbels, and is pierced by a raised portal, an oculus and two Apulian-style biforas. The building consists of the church and a crypt beneath the presbytery.

The monastery is first documented in a decree of Pope Lucius II dated 19 January 1184, issued to settle a dispute that arose in 1183 between Oderisio, bishop of Penne, and Senebaldo, abbot of San Quirico in Antrodoco. The pope entrusted the case to Cardinal Ottavio of Santi Sergio e Bacco and Teodino, bishop of Porto. The document proves the complex already existed in the 12th century; the church and its crypt were built between the 11th and 13th centuries.

The complex belonged to an abbey whose ruins still flank the church, and it is listed among the monumental buildings of the province of Teramo. It now forms part of the Valle delle Abbazie, a religious tourist route that also takes in Santa Maria di Ronzano, mentioned with it in the same 1184 papal decree.

The church stands isolated on a small hill above the Mavone river, near Isola del Gran Sasso d'Italia; it is reached by a path off the road through the Mavone valley. The building is part of the Valle delle Abbazie religious itinerary, and the ruins of the adjoining abbey lie around it. The interior is entered from the raised main portal up several steps.

The church is also called San Giovanni al Mavone, after the river it overlooks. Local historians Vincenzo Balzano and Ignazio Carlo Gavini disagreed about the crypt: Balzano saw it as a pre-1000 church later enclosed, Gavini as part of one design built in stages.