The Church of Santa Maria in Sperlonga, formerly known as Sancta Mariae de Sperlonche, is the oldest religious building in the village and was already one of the most important places of worship in the area by the 12th century, as attested by a document from 1135 in the Codex Caietanus. Today, following a long period of neglect and a thorough restoration, it is used as a venue for cultural events and performances.

The interior features a two-nave layout, the result of successive extensions over the centuries. Near the high altar stands a painting depicting the Assumption, flanked by a vaulted choir. Among the most significant areas is the Nativity Chapel, dating back to the 18th century, whilst the side aisle preserves 12th-century frescoes, precious examples of the ancient pictorial decoration. On the right-hand side of the central nave there is also a statue of the Neapolitan school.

Over time, the parish function was transferred to the new Church of Santa Maria Assunta in Cielo, built in the 20th century in a modern style and situated in Piazza Europa, to meet the needs of a growing community and the increase in tourism in the area.

Despite this change of use, the ancient church of Santa Maria retains great historical and cultural value, representing one of the most significant testimonies to the religious history of Sperlonga and its connection with the area between Terracina, Fondi and Gaeta.