The Diocese of Saint Joseph (Latin: Dioecesis Sancti Iosephi) was a Latin Church ecclesiastical territory or diocese of the Roman Catholic Church in the northwestern part of the state of Missouri in the United States, erected on March 3, 1868, with territories taken from the Archdiocese of Saint Louis. Its first bishop was John Joseph Hogan. On July 2, 1956, the diocese lost territory to the newly erected Diocese of Jefferson City and the Diocese of Springfield–Cape Girardeau. On that date it was united to the Diocese of Kansas City, which was renamed the Diocese of Kansas City–Saint Joseph.

After the founding of Saint Joseph, MO by Joseph Rubidoux in 1843, the first Catholic church in the town was built in 1847. It's first pastor was Rev. Thomas Scanlon. In September of 1847, this church was dedicated by the Archbishop of St. Louis, Archbishop P.R. Kenrick. During the Second Plenary Council of Baltimore in 1866, St. Joseph was proposed to become its own diocese. This diocese would encompass the portion of Northern Missouri that lies between the Missouri and Chariton rivers. It's first Bishop was chosen on March 3, 1869 as Bishop John Joseph Hogan. The same year, ground broke for a cathedral.

On September 10, 1800 Bishop Hogan was transferred to the Diocese of Kansas City and Bishop Maurice Francis Burke was moved from the Diocese of Cheyenne, Wyoming to take his place.

As of 1911, the diocese had accumulated 8 parishes, 12 priests, 6 parish schools, a college created by the Christian Brothers, and a school for young women created by the Sisters of Charity. The diocese had a catholic population of around 10,000 people.

Shorty after Bishop LeBlond resigned from his position, the diocese was united with the Diocese of Kansas City to form the Diocese of Kansas City-Saint Joseph on July 2, 1956.

• John Joseph Hogan (1868–1880); appointed Bishop of Kansas City but continued here as Apostolic Administrator, 1880–1893
• Maurice Francis Burke (1893–1923); died
• Francis Gilfillan (1923–1933); died
• Charles Hubert Le Blond (1933–1956); resigned

• Francis Gilfillan (1922-1923)

• Francis Johannes, appointed Coadjutor Bishop of Leavenworth in 1927
• Charles Francis Buddy, appointed Bishop of San Diego in 1936

• Diocese of Kansas City–Saint Joseph
• Catholic Hierarchy Profile of the Diocese of Saint Joseph
• Article in the Catholic Encyclopedia

39°45′29″N 94°50′12″W / 39.75806°N 94.83667°W / 39.75806; -94.83667