The Diocese of Biloxi (Latin: Dioecesis Biloxiensis) is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church that encompasses 17 counties in southern Mississippi in the United States. The diocese was erected on March 1, 1977, when it was split from the Diocese of Jackson. The Diocese of Biloxi is a suffragan diocese of the ecclesiastical province of the metropolitan Archdiocese of Mobile, though for its first three years the diocese was in the province of the Archdiocese of New Orleans.

The Cathedral of the Nativity of the Blessed Virgin Mary in Biloxi, Mississippi, is the diocesan cathedral.

The first Catholic priests in Mississippi were French Jesuit and Capuchin missionaries who accompanied the La Salle, Marquette, and d'Iberville expeditions in the 17th and 18th centuries. In 1787, three priests, Fathers McKenna, White, and Savage, arrived in Natchez from Spain and erected three missions in the vicinity. These missions disappeared after the Spanish Empire ceded the area to the new United States in the early 19th century.

The Mississippi Territory was originally under the jurisdiction of the Diocese of Louisiana and the Two Floridas. In 1826, Pope Leo XII moved the new state of Mississippi into the Vicariate Apostolic of Mississippi. The pope named Bishop Louis-Guillaume-Valentin DuBourg as the vicar apostolic. In 1837, Pope Gregory XV elevated the vicariate to the Diocese of Natchez, encompassing all of Mississippi. The Biloxi area would remain part of this diocese, succeeded by the Diocese of Natchez-Jackson, for the next 140 years.

When Bishop John J. Chanche of Natchez visited the Mississippi Gulf Coast in 1841, there were no Catholic churches or schools anywhere in the state. The first Catholic church in Biloxi, Nativity Blessed Virgin Mary (BVM), was constructed in 1843. St. Stanislaus College, a boarding school for boys, was established in 1854 in Bay St. Louis by the Brothers of the Sacred Heart.

Missionary priests established a small chapel in Pascagoula in 1859. The first Catholic high school in Biloxi, Sacred Heart Academy, opened in 1875. Resurrection Catholic School was started in Pascagoula in 1882 in by the Sisters of Perpetual Adoration. In 1898, the first Catholic church in Gulfport, St. James, was dedicated. Sacred Heart School was founded in 1900 in Hattiesburg by the Sisters of Mercy. St. John High School in Gulfport opened in 1900.

Pope Paul VI erected the Diocese of Biloxi, with territory taken from the Diocese of Natchez-Jackson on March 1, 1977. The pope appointed Auxiliary Bishop Joseph Lawson Howze of Natchez-Jackson as the first bishop of Biloxi. He became the first African-American to be appointed a Catholic bishop in the 20th century.

In 1980, Pope John Paul II elevated the Diocese of Mobile to a metropolitan archdiocese and designated the Diocese of Biloxi as a suffragan of the new metropolitan see. Howze retired in 2001 after 24 years as bishop of Biloxi.

To replace Howse, John Paul II appointed Monsignor Thomas John Rodi of New Orleans as the next bishop of Biloxi in 2001. In 2007, the diocese was sued by 157 members of the former St. Paul Parish in Pass Christian. After their church was destroyed by Hurricane Katrina in 2005, Rodi incorporated St. Paul into a new parish and decided to build a new church in a different location. The plaintiffs wanted the funds raised for the new church to be used to build it on the original site. After going through the lower courts, the Mississippi Supreme Court dismissed the lawsuit in 2014. Rodi served in Biloxi until 2008, when he was named archbishop of Mobile.

Auxiliary Bishop Roger Morin was named the third bishop of Biloxi by Pope Benedict XVI in 2009. In 2016, Morin resigned.

As of 2023, the current bishop of the Diocese of Biloxi is Louis Kihneman III. formerly of the Diocese of Corpus Christi. He was appointed by Pope Francis in 2016.

1. Joseph Lawson Howze (1977–2001)
2. Thomas John Rodi (2001–2008), appointed Archbishop of Mobile
3. Roger Morin (2009–2016)
4. Louis Frederick Kihneman (2017–present)

Ronald Paul Herzog, appointed Bishop of Alexandria in 2004

The Diocese of Biloxi has nine elementary schools, four middle/high schools and one high school.

• Our Lady Academy Middle/High School – Bay St. Louis
• Resurrection Catholic Middle/High School – Pascagoula
• Sacred Heart Catholic School – Hattiesburg
• St. Patrick Catholic Middle/High School – Biloxi
• Saint Stanislaus College – Bay St. Louis

These two schools closed in 2007, replaced by St. Patrick Catholic Middle/High School:

• Mercy Cross High School – Biloxi
• St. John High School – Gulfport

Several diocesan priests have been credibly accused of sexual misconduct involving minors. These cases go back to the founding of the diocese in 1977. Bishop Kihneman acknowledged three of these names as credibly accused of sexual misconduct of minors in 2019, but recognized that this was a “small, belated step forward.” The following priests were listed by the diocese as having credible accusations of sexual abuse of minors.

• Jerome J. Axton: A diocesan priest serving at Nativity BVM Cathedral from 1983 to 1988. In 1989, a woman reported to the diocese that she had been sexually assaulted by Axton when she was a teenager between 1985 and 1986. The diocese notified law enforcement and permanently suspended Axton from ministry in 1992. Axton died in 2020.
• Joseph A. Romansky: An extern priest from the Diocese of Cleveland working in Biloxi from 1988 to 1992. Romansky was assigned to Our Lady of Fatima in Biloxi. In 1985, Romansky pleaded guilty in Cleveland to disseminating material and-or performance harmful to juveniles. He had been accused of maturbating in front of several teenage boys. Despite his record, Bishop Howze in 1988 allowed Romansky to work in the Diocese of Biloxi for four years. He died in 2004. In 2022, a man reported to the diocese that Romansky had sexually abused him when he was nine years old in 1989 in Biloxi.
• Jose Vazquez Morales: A diocesan priest working in Laurel, Hattiesburg, Wiggins, and Lucedale. Morales was caught abusing a 12-year-old boy when "the boy's mother found the two engaged in a sexual act at the family's home". In 2016, Morales pleaded guilty to sexual abuse charges and was sentenced to ten years in prison with deportation with deportation to Mexico after his release from prison.
• Vincent D. Dilalla: A diocesan priest assigned to St. Alphonsus in Ocean Springs (1980-1981), and Nativity BVM (1981-1983). In 2021, a man reported to the diocese that he had been sexually assaulted by DiLalla when he was 12 years-old in Gulfport. Dilalla died in 1990.
• Vincent The Quang Nguyen: An extern priest serving at St. Michael's Church in Biloxi from 1986 to 1989. In 1989, several parents accused Nguyen of sexually abusing their daughters. The parents also reported the misconduct to the Biloxi Police Department, but no charges were filed. The diocese permanently suspended Nguyen from ministry in 1989.

Any cases prior to 1977 are acknowledged by the Catholic Diocese of Jackson.

In 2019, the diocese was sued by man who claimed that he had been sexually assaulted when he was 12 years old in the mid-1980s by Reverend John Scanlon, then serving at Sacred Heart Church in Hattiesburg. The alleged assaults occurred at the rectory after the boy finished catechism class. Scanlon died in 1995. A lower court dismissed the case due to the passage of the statute of limitations, but that ruling was reversed by the Mississippi Supreme Court in 2021. The Supreme Court sent the case back to lower courts for trial.

• Catholic Church by country
• Catholic Church hierarchy
• List of the Catholic dioceses of the United States

• Roman Catholic Diocese of Biloxi Official Site
• Cathedral of the Nativity of the Blessed Virgin Mary

30°24′43″N 88°55′40″W / 30.41194°N 88.92778°W / 30.41194; -88.92778