St Mary's Cathedral, Perth, officially the Cathedral of the Immaculate Conception of the Blessed Virgin Mary, is the cathedral church of the Roman Catholic Archdiocese of Perth, and seat of its Archbishop, currently Timothy Costelloe. The cathedral is at the centre of Victoria Square, on the northern end of Victoria Avenue, Perth, Western Australia. The cathedral as it now stands was constructed in three main phases, with the first phase completed in 1865.