Troia Cathedral (Italian: Concattedrale di Troia; Cattedrale di Santa Maria Assunta) is the cathedral of Troia in Apulia, Italy, dedicated to the Assumption of the Blessed Virgin Mary. Built in the first quarter of the 12th century, it is reckoned a masterpiece of Apulian Romanesque architecture and is particularly noted for the rose window and the bronze doors of the west front. Formerly the seat of the Bishops of Troia, it is now a co-cathedral in the diocese of Lucera-Troia.
The church is located in the centre of Troia on the Via Regina Margherita. The principal façade, orientated to the north-west, looks onto a small forecourt. The dedication to the Assumption of the Virgin Mary was taken over from the predecessor building, which has been partly incorporated into the present structure.
The following Latin inscription is located on a wall of the Chapel of the Patron Saints: Felix antistes dom(i)nus Guillelmus secundus fecit hanc aede(m) D(e)o ac beatae Mariae vobisq(ue) fidelibus felices troiani
A Byzantine church formerly stood on the site, apparently constructed largely from the remains of Roman buildings. Work on a new cathedral began in the last quarter of the 11th century. The year 1073 is often given but the exact date of the start of construction is in fact unconfirmed. Excavations in the 1950s were at one time believed to have established that the present transept was originally the nave of the previous church building, but this is now contested. It is however certain that the cores of the two western pillars of the crossing date from the very first building phase, and possibly served the same purpose in the original church.