| Castelló Co-Cathedral | |
| Fullname: | Co-Cathedral of Saint Mary |
| Other Name: | Spanish; Castilian: Concatedral de Santa María |
| Coordinates: | 39.986°N -0.037°W |
| Location: | Castelló de la Plana |
| Country: | Spain |
| Denomination: | Catholic |
| Address: | 9, Plaça Major |
| Status: | Cathedral |
| Dedication: | Mary, mother of Jesus |
| Architect: | Vincente Traver Tomás |
| Style: | Gothic Revival |
| Bells Hung: | --> |
| Metropolis: | Valencia |
| Diocese: | Segorbe-Castellón |
| Bishop: | Casimiro López Llorente |
The Co-cathedral of Saint Mary (Catalan; Valencian: Cocatedral de Santa Maria, Spanish; Castilian: Concatedral de Santa María) is the cathedral of Castelló de la Plana, located in the comarca of Plana Alta, in the Valencian Community, Spain.