Archbishop Timothy Costelloe, 58, succeeds Archbishop Barry James Hickey, who resigned for reasons of age.
The Archdiocese of Perth has a population nearly 1.7 million, with some 415,000 Catholics. They are served by about 265 priests and more than 600 religious.
And in Houston, Texas, a member of the local archdiocesan clergy has been named auxiliary bishop.
Bishop-designate George Sheltz, 65, will assist Cardinal Daniel DiNardo in the Archdiocese of Galveston-Houston, which has some 1.2 million Catholics in a population of nearly 6 million.
They are served by about 430 priests and more than 350 permanent deacons, as well as more than 680 religious.
