John Joseph Cantwell was an Irish-born American prelate of the Catholic Church. He led the Archdiocese of Los Angeles from 1917 until his death in 1947, becoming its first archbishop in 1936. Cantwell was critical of the U.S. film industry and helped found the National Legion of Decency.

The Archdiocese of Los Angeles is a Latin Church ecclesiastical territory or archdiocese of the Catholic Church located in the southern portion of the U.S. state of California. The archdiocese's cathedra is in Los Angeles, the archdiocese comprises the California counties of Los Angeles, Santa Barbara and Ventura. The cathedral is the Cathedral of Our Lady of the Angels in Los Angeles, and its present archbishop is José Horacio Gómez Velasco. With over five million professing members and weekly liturgies celebrated in 32 languages, the Archdiocese of Los Angeles is numerically the single largest and most ethnically diverse archdiocese in the United States.