St. Joseph Cathedral is a Catholic cathedral located in downtown Baton Rouge, Louisiana, United States. It is the mother church of the Diocese of Baton Rouge, and it has been listed on the National Register of Historic Places since 1990.
St. Joseph Parish was founded as the Parroquia de Nuestra Señora de los Dolores in 1792; its name was changed some time after Louisiana became a State in 1812 as English became more and more the language of the population in Baton Rouge. The present church building, the Parish's third, was begun in 1853.
The church was designated the cathedral church of the Diocese of Baton Rouge by Blessed John XXIII in the bull of erection "Peramplum Novae Aureliae" dated July 22, 1961; the erection of the diocese took place on November 8, 1961, with Most Rev. Robert Emmet Tracy as is first bishop. The church building underwent a significant interior renovation in 1967 and was re-dedicated on September 30, 1970.