Chiesa di San Nicolò Regale, Norman church in Mazara del Vallo, Italy.

San Nicolò Regale is a church with a square floor plan in Mazara del Vallo. The interior is supported by four central columns and topped by a large dome resting on a low, wide drum, with three apses at the rear.

Built in 1124, the church was transformed between the 17th and 18th centuries to suit Baroque canons, becoming octagonal with a pitched roof. A 1947 attempt to restore its original forms failed; only in the 1980s did it regain its medieval Arab-Norman appearance. It is documented as a seat of the Equestrian Order of the Holy Sepulchre of Jerusalem.

The floor carries a coloured design of Islamic inspiration, and the church is documented as a seat of the Equestrian Order of the Holy Sepulchre of Jerusalem. Its square plan, three apses and hemispherical dome link it to San Cataldo in Palermo and the Santissima Trinità di Delia at Castelvetrano, built in the same period.

The church stands on the left bank of the Mazaro, in the historic centre of Mazara del Vallo, and is reached on foot through the surrounding lanes. It is a small building with a single hall, so a visit takes only a short time; check locally before setting out, as access depends on the parish rather than on fixed visiting hours.

The 1933 excavation found traces of late-imperial Roman mosaics in the base beneath the church, a layer older than the 1124 building itself. The same base is what visitors see under the Norman walls, so the Roman phase is easy to miss.