High Quality Content by WIKIPEDIA articles! The Catholic Church in Australia is part of the worldwide Catholic Church, under the spiritual leadership of the Pope and Curia in Rome.There are an estimated 5.1 million baptised Catholics in Australia, 26% of the population, a plurality, making it Australia's largest single Christian denomination (larger than Anglicans and Uniting combined). In the Catholic Church, a province is a grouping of several neighbouring dioceses. The senior diocese is known as metropolitan, while the others are known as suffragan.