Alghero Cathedral, otherwise the Cathedral of St. Mary the Immaculate (Italian: Duomo di Alghero; Cattedrale di Santa Maria Immacolata Catalan: Catedral de l'Alguer; Catedral de Santa Maria Immaculada), is a Roman Catholic cathedral in Alghero in the province of Sassari, Sardinia, Italy. It is located in the historic center of the city.