St Mary's Cathedral College (SMCC) is a private, Catholic, secondary day school for boys, located in the Central Business District of Sydney, New South Wales, Australia. Founded in 1824, St Mary's currently caters for approximately 750 students from Years 5 to 12, and is attached to St Mary's Cathedral. The school is currently serviced by the Congregation of Christian Brothers and was the last school in Sydney to be served by Christian Brothers as both Principal and Deputy Principal. St Mary's Cathedral College was established in 1824 as an elementary school by Reverend John Therry. The high school was established in 1828. It is the oldest Catholic school in Australia. St Mary's Cathedral College is conducted by the Christian Brothers and administered by the Catholic Education Office, Eastern Region. The Christian Brothers association with the school dates back to 1911. Catholic education on the same site as St Mary's Cathedral has been continuous since 1824, except during the construction of the existing College buildings and the associated Bishops quarters (1987–1991).