Patrick William Riordan was a Canadian-born American prelate of the Catholic Church who served as Archbishop of San Francisco from 1884 until his death in 1914. He served during the 1906 San Francisco earthquake, and he was a prominent figure in the first case submitted to the Permanent Court of Arbitration.

The Archdiocese of San Francisco is a Latin Church ecclesiastical territory or diocese of the Catholic Church in the northern California region of the United States. The Archdiocese of San Francisco was erected on July 29, 1853, by Pope Pius IX and its cathedral is the Cathedral of Saint Mary of the Assumption.