Nostra Segnora de Mesumundu ("Our Lady of Mesumundu") is a religious building in the territory of Siligo, Sardinia, Italy. Located in the archaeological complex with the same name, it was built in the 6th century, during the Byzantine domination of the island, over a pre-existing Roman structure (2nd century AD). The Byzantines re-used part of the walls of the Roman building, as well as the aqueduct. According to some sources, the edifice could have been used as a baptistery.