
At the time, the region was part of the Las Californias province of New Spain. The Catholic presence in present-day Orange County dates to the 1776 establishment of Mission San Juan Capistrano, a Spanish mission founded by Father Junipero Serra and the Franciscan order. Holy Family Cathedral in Orange was the diocese's first cathedral. The diocesan patron saints are Our Lady of Guadalupe and Andrew Dũng-Lạc. It also sponsors a variety of programs and activities in conjunction with other local organizations. In addition to its 56 parish churches, the diocese oversees 41 schools and three general hospitals, plus one disabled and five ethnic ministry centers. Diocesan offices are situated at the Christ Cathedral campus in Garden Grove, California. The current diocesan bishop is Kevin Vann, who was installed on December 10, 2012. The diocesan cathedral is the Christ Cathedral in the Garden Grove.

It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Los Angeles. The Diocese of Orange was erected in 1976. It is sometimes referred to as the Diocese of Orange in California, to avoid confusion with the Diocese of Orange in Orange, France, which was dissolved in 1801. The Diocese of Orange ( Latin: Dioecesis Arausicanae in California Spanish: Diócesis de Orange Vietnamese: Giáo phận Quận Cam) is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church that covers all of Orange County, California, in the United States.
