Saint-Florent Cathedral or Nebbio Cathedral (Cathédrale Santa-Maria-Assunta,[1] also known as Cathédrale du Nebbio) is a former Roman Catholic church located in the town of Saint-Florent in Corsica, France.

The ancient region of the Nebbio, or Nebbiu, on Corsica formed a Christian bishopric from the 5th century onwards.

The former cathedral, now the church of Santa Maria Assunta, located at the edge of the town of Saint-Florent on the road that leads to Poggio d'Oletta, is a heavily-restored Romanesque structure.

Because of the insecurity of the coasts and the malaria which was endemic in the marshes that surrounded the foot of the hill on which the cathedral stands, it was abandoned by the bishops.

At the beginning of the 16th century the humanist Agostino Giustiniani, bishop of Nebbio, had the cathedral repaired.