The 18th-century Cathedral of St John the Baptist is Sligo's Anglican cathedral. The Cathedral of the Immaculate Conception was almost certainly built on the site of a medieval hospital and parish church in honour of the Trinity, founded in the 13th century. Part of the medieval structure is included in the present west tower. When the German-born Irish architect Richard Cassels (1690-1751) came to Sligo in 1730 to design Hazelwood House for the Wynne family, he was also commissioned to build St John's Church.
The Cathedral of the Immaculate conception is famous for being the only Norman-style church in Ireland. The church was constructed in 1874 by the Bishop of Elphin, upon deciding that the local diocese was in need of a larger space. It is also notable for its impressive spire and large apse in the sanctuary.
St. Crumnathy's Cathedral is a former cathedral built in 1822. It was deconsecrated after it was closed for worship in 1997.