The Church of Santa Maria dell'Ammiraglio or San Nicolò dei Greci, commonly called the Martorana, overlooking the renowned Piazza Bellini in Palermo, Sicily, southern Italy
. Co-Cathedral of Eparchy of Eastern Rite, is part of the Italo-Albanian Catholic Church, Diocese Byzantine-Greek Rite of Piana degli Albanesi.
The original church was built in the form of a compact cross-in-square ("Greek cross plan"), a common south Italian and Sicilian variation on the standard middle Byzantine church type.
The church is renowned for its spectacular interior, which is dominated by a series of 12th century mosaics executed by Byzantine craftsmen. The mosaics show many iconographic and formal similarities to the roughly contemporary programs in the Cappella Palatina, in Monreale Cathedral and in Cefalù Cathedral, although they were probably executed by a distinct atelier.