The Diocese of Stockton (Latin: Diœcesis Stocktoniensis) is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in the Central Valley and Mother Lode region of California in the United States. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archbishop of San Francisco

The mother church of the Diocese of Stockton is the Cathedral of the Annunciation in Stockton.

As of 2015^[update], the Diocese of Stockton served 250,692 Catholics (18.4% of 1,361,162 total) on 15,995 km² in 35 parishes. It had 97 priests (83 diocesan, 14 religious), 51 deacons, 66 lay religious (15 brothers, 51 sisters), six seminarians and 12 missions.^[1]

The covers the counties of Alpine, Calaveras, Mono, San Joaquin, Stanislaus and Tuolumne, with most of the diocese population living in the San Joaquin Valley. The diocese provides service to the many migrant camps in the region.

The largest racial/ethnic groups in the diocese are White and Hispanic. The largest Azorean Portuguese population outside the Azores is found in the diocese. It is estimated that 60% of the diocesan Catholic population is Hispanic.

The largest Asian community in the diocese is Filipino, followed by the Vietnamese community. The USCCB statement Asian and Pacific Presence^[2] lists the diocese of Stockton as among the top thirty dioceses in the United States with the highest Asian and Pacific Island population. Mass is celebrated over 180 times each Sunday in English, Spanish, Portuguese, Latin and Laotian. Weekday masses are celebrated in these languages and Vietnamese.

Pope John XXIII erected the Diocese of Stockton on January 13, 1962, taking its territory from the Archdiocese of San Francisco and the Diocese of Sacramento. The pope named Auxiliary Bishop Hugh Donohoe of San Francisco as the first bishop of Stockton.^[3] In 1966, the Vatican transferred several more counties from Sacramento to the Diocese of Stockton. Donohoe became bishop of the Diocese of Fresno in 1969.^[3]

The second bishop of Stockton was Auxiliary Bishop Merlin Guilfoyle of San Francisco, appointed by Pope Paul VI in 1969.^[4] Guilfoyle retired in 1979. To replace Guilfoyle, Pope John Paul II selected Auxiliary Bishop Roger Mahony of Fresno in 1980. Five years later, in 1985, Mahony became archbishop of the Archdiocese of Los Angeles.^[5]

Auxiliary Bishop Donald Montrose of Los Angeles was the next bishop of Stockton, named by John Paul II in 1985.^[6] Montrose focused on getting Spanish-speaking priests in the diocese, traveling to Mexico, Colombia and other Latin American countries to recruit them. In 1988, Montrose succeeded in persuading the Sisters of the Cross to relocate to Modesto from Mexico.^[7] Montrose retired in 1999.

John Paul II appointed Auxiliary Bishop Stephen Blaire of Los Angeles in 1999 as the new bishop of Stockton.^[8] In 2014, the diocese filed for Chapter 11 Bankruptcy, which was later granted in 2017.^[9] As a result of the bankruptcy agreement, approximately $15 million was to be paid to sexual abuse victims of diocesan clergy.^[10] Blaire retired in 2018.

As of 2023, the current bishop of the Diocese of Stockton is Myron J. Cotta, formerly an auxiliary bishop from Sacramento. He was appointed by Pope Francis in 2018.^[11]

The Diocese of Stockton consists of eight deaneries. ^[17]

• Communion and Liberation – St. Luke's Catholic Church
• Dominican Sisters of San Rafael – St. Joseph's Medical Center, Stockton
• Legion of Mary – active at numerous parishes
• Newman Center – University of the Pacific / San Joaquin Delta College, Stanislaus State University
• Oblates of St. Francis de Sales – St. Mary's High School, Stockton