Insigne collegiata parrocchiale di Santa Maria Maggiore, Collegiate church in Guglionesi, Italy.

The Insigne Collegiata di Santa Maria Maggiore is a church with a Latin cross layout and three naves, marked by semicircular apses along its western end. Its Baroque facade on Piazza XXIV Maggio is divided into three sections by mixed-line pilasters and features a central entrance.

The church was built in the 11th century following a vow made by Norman leader Robert Guiscard to the Madonna after his forces conquered the area in 1060. In the following century it gained further importance when the relics of Saint Adam the Abbot arrived, transforming it into a pilgrimage site.

The church is dedicated to Santa Maria Maggiore, but the town's patron is Saint Adam the Abbot, whose relics were moved here on the night of 2–3 June 1102. His silver statue, weighing 33 kg, was made in 1886 and stands near the altar in the crypt. A 1587 fresco cycle in the crypt depicts scenes from his life.

The church sits centrally on Piazza XXIV Maggio and is easily reached on foot from the town center. As an active place of worship, visitors should observe appropriate behavior and dress when entering.

The crypt, reached from the right nave, keeps the relics of Saint Adam the Abbot and a 1740 gilded wooden altarpiece showing his ecstasy against a medieval view of Guglionesi. On its vaults survive two 16th-century frescoes with Old Testament scenes, the Flood and the Tower of Babel; Genesis episodes fill an adjoining room's false coffered ceiling.