The Diocese of Columbus (Latin: Dioecesis Columbensis) is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church covering 23 counties in central Ohio in the United States. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Cincinnati.

The mother church of the Diocese of Columbus is St. Joseph Cathedral in Columbus. The diocese was erected on March 3, 1868, by Pope Pius IX. The current bishop of Columbus is Earl K. Fernandes.

The Diocese of Columbus contains 108 parishes in 23 counties:

Coshocton, Delaware, Fairfield, Fayette, Franklin, Hardin, Hocking, Holmes, Jackson, Knox, Licking, Madison, Marion, Morrow, Muskingum, Perry, Pickaway, Pike, Ross, Scioto, Tuscarawas, Union, and Vinton.

During the 17th century, present day Ohio was part of the French colony of New France. The Diocese of Quebec, had jurisdiction over the region. However, unlike other parts of the future American Midwest, there were no attempts to found Catholic missions in Ohio.

In 1763, Ohio Country became part of the British Province of Quebec, forbidden from settlement by American colonists. After the American Revolution ended in 1783, Pope Pius VI erected in 1784 the Prefecture Apostolic of the United States, encompassing the entire territory of the new nation. In 1787, the Ohio area became part of the Northwest Territory of the United States. Pius VI created the Diocese of Baltimore, the first diocese in the United States, to replace the prefecture apostolic in 1789.

In 1808, Pope Pius VII erected the Diocese of Bardstown in Kentucky, with jurisdiction over the new state of Ohio along with the other midwest states. Dominican priests from Bardstown were the first missionaries and clergy in the Columbus area. The first Catholic chapel built in Ohio was a log structure in Perry County; it was dedicated in 1818 by Edward Fenwick.

Pope Pius VII in 1821 erected the Diocese of Cincinnati, taking all of Ohio from Bardstown. The visit of Cincinnati Bishop John Purcell to central Ohio in June 1836, began the activity of the Catholic Church in the city of Columbus. After saying Mass in a house on Canal Street on June 5, Purcell asked the Catholic men in attendance to meet regarding the construction of a church. They developed a plan to build a church on a lot already owned by the Catholics of the area—where Holy Cross Church now stands. In 1837, the diocese sent a resident pastor, Henry Juncker, to cover the Columbus and Chillicothe areas. Juncker built Holy Cross Church, opening it in 1838 with a Sung Mass. By 1843, Holy Cross parish was scheduling multiple masses on Sundays and building a school.

At the close of the Second Plenary Council of Baltimore in 1866, the American bishops petitioned Pope Pius IX to establish a new diocese with its seat in Columbus. On March 3, 1868, the pope erected the Diocese of Columbus, encompassing the portions of Ohio "...lying south of 40' and 41" and between the Ohio River on the East and the Scioto River on the West together with the Counties of Franklin, Delaware and Morrow." Pius IX appointed Auxiliary Bishop Sylvester Rosecrans of Cincinnati as the first bishop of Columbus.

When the Diocese of Columbus was erected, it had only three churches, all in the city of Columbus: Holy Cross, St. Patrick's, and St. Mary's. The diocese was mostly agricultural, having been settled first by Maryland and Pennsylvania residents who had moved west, and then later by German and Irish immigrants. Rosecrans established the Catholic Columbian, a newspaper for the diocese, in addition to opening St. Aloysius Seminary and St. Vincent's Orphan Asylum. He oversaw the construction of St. Joseph Cathedral to its consecration in 1878, before dying the following morning.

To replace Rosencrans, Pope Leo XIII appointed John Watterson as the second bishop of Columbus in 1880. The major challenge facing the diocese was the debt accrued by the construction of St. Joseph. During his 19-year-long tenure, Watterson increased the number of priests and schools in the diocese, oversaw the building of two hospitals and the Pontifical College Josephinum in Columbus and erected many new missions and parishes.

On April 6, 1900, Henry K. Moeller, chancellor of the Archdiocese of Cincinnati, was appointed the third bishop of Columbus by Leo XIII. During his episcopacy, the diocesan debt was split among the parishes and nearly eliminated in three years and a diocesan synod was convened. Moeller also established missions, parishes, and schools to serve the increasing immigrant population of the Diocese. Moeller was appointed as the coadjutor bishop of Cincinnati by Pope Pius X in 1903.

Moeller's replacement, James Hartley, was appointed bishop in 1903. During his tenure, Hartley oversaw a significant growth of the diocese In 1905, he erected his first parishes, Holy Rosary and St. Aloysius. In 1906, he retired the debt on St. Joseph Cathedral. Within the first five years of his episcopate, Hartley began or dedicated over 25 churches, schools, and chapels. He established the following institutions:

• St. Charles Seminary in Columbus
• St. Joseph Cemetery in Lockbourne
• St. Ann Hospital in Westerville
• Mercy Hospital in Portsmouth
• Good Samaritan Hospital in Zanesville
• Mercy Hospital in Mount Vernon
• St. Therese Shrine in Columbus

Toward the end of his term as bishop, Hartley consecrated Edward Hettinger as the first auxiliary bishop of the Columbus diocese. Hartley died in 1944.

Pope Pius XII appointed Michael Ready as bishop of Columbus in 1945. That same year, the Holy See established the Diocese of Steubenville, removing 13 counties from the Diocese of Columbus to form the new diocese. At the same time, nine counties were added to the Diocese of Columbus from the Archdiocese of Cincinnati.

One of Ready's first tasks was overseeing the erection of the new Diocese of Steubenville. He established the Catholic Welfare Bureau and appointed a director of charities for the diocese. Ready was a critic of the Ohio State University board of trustees' decision in 1951 that required all campus speakers be cleared by University President Howard L. Bevis in advance.

Ready also organized the Holy Name Society, a Parent-Teacher Organization, the Council of Catholic Women, the Catholic Youth Council, and the St. Vincent de Paul Society in the diocese. He created 18 new parishes and oversaw the construction of nine elementary and five high schools. Ready founded two nursing homes, the diocesan Child Guidance Center, and the Catholic Student Center at Ohio State University. He worked with his fellow Ohio bishops to start the Ohio Catholic Welfare Conference. Ready died in 1957.

Pope Pius XII appointed Auxiliary Bishop Clarence Issenmann of the Archdiocese of Cincinnati as the sixth bishop of Columbus on December 5, 1957. As bishop, Issenmann established the Diocesan Development Fund so as to supply for the expansion of the diocese, which added eight parishes and six high schools under Issenmann. He also found a new building to house diocesan offices, and offered a televised Mass every week. Pope Paul VI named him as coadjutor bishop of the Diocese of Cleveland in 1964.

Bishop John Carberry from the Diocese of Lafayette in Indiana was appointed the seventh bishop of Columbus by Pope Paul VI on January 16, 1965. As bishop, he implemented the reforms of the Second Vatican Council and supported the Civil Rights Movement and ecumenical movement. He established the Clergy Advisory Council, and oversaw the renovation of St. Joseph's Cathedral after issuing regulations for liturgical changes. Carberry also bought a new building to centralize the offices of the diocesan chancery. He helped found the Inter-Church Board for Metropolitan Affairs, the first organization in the United States uniting Protestants and Catholics for ecumenism and social action. In January 1968, he became the first Catholic bishop to receive the Ohio Council of Churches' annual "Pastor of Pastors" award. Carberry was named archbishop of the Archdiocese of St. Louis in 1968.

Paul VI named Auxiliary Bishop Clarence Elwell from the Diocese of Cleveland as the eighth bishop of Columbus in 1968. During his tenure as bishop, Elwell continued the implementation of the reforms of the Second Vatican Council, initiated under Carberry. An advocate of Catholic education, he opened the following schools in Ohio:

• Tuscarawas Central Catholic High School in New Philadelphia
• William V. Fisher Catholic High School in Lancaster
• Bishop Rosecrans High School in Zanesville

Elwell also converted the diocesan seminary in Columbus into St. Charles College Preparatory School. He also established Resurrection Cemetery in Lewis Center, Ohio, St. Peter Parish in Worthington, Ohio, the Sisters' Council, and the Pastoral Council. He significantly expanded the Development Office, the Parish Aid Fund, and the diocesan self-insurance program. Elwell died in 1973.

Auxiliary Bishop Edward Herrmann from the Archdiocese of Washington was appointed bishop of Columbus in 1973, by Paul VI. Herrmann helped establish Operation Feed in Columbus, a countywide food drive that now provides millions of meals every year to people in the Columbus area. He also reorganized the diocese into the 15 vicariates and instituted the Emmaus Spirituality Program for priests. Hermann died in 1982.

In 1983, Pope John Paul II appointed Auxiliary Bishop James Griffin from the Diocese of Cleveland as the tenth bishop of the Diocese of Columbus. In 1985, Griffin established the Foundation of the Catholic Diocese of Columbus and initiated the Legacy of Catholic Learning campaign in 1989 and Challenge In Changing Times campaign. He also established "Breaking The Silence" task force to reduce family violence. Griffin also served on a number of committees of the United States Conference of Catholic Bishops and was president of Catholic Relief Services (1991–1995). In 2004, after 21 years as bishop of Columbus, Griffin retired.

In 2004, John Paul II appointed Auxiliary Bishop Frederick F. Campbell from the Archdiocese of St. Paul and Minneapolis as the eleventh bishop of Columbus. In 2005, Campbell proposed the establishment of a civil registry of priests from the diocese of Columbus who had been "credibly accused" of sexual abuse. Campbell spoke out in 2006 against a proposed law in the Ohio General Assembly that would have allowed a 20-year statute of limitations for sexual abuse cases. In his testimony to the legislature, Campbell claimed that the 20-year window for prosecution wasn't fair and would curtail the church's charitable work. In the end, the assembly passed the legislation with a 10-year window.

In April 2013, the diocese fired Carla Hale, a teacher at Bishop Watterson High School in Columbus. The diocese took action after receiving a complaint that Hale had a domestic partner who was a woman. Hale then threatened to file a complaint with the City of Columbus under its anti-discrimination ordinances. Hale and the diocese later reached a settlement in which she would not return to Bishop Watterson.

After Campbell resigned in 2019, Pope Francis appointed Auxiliary Bishop Robert J. Brennan from the Diocese of Rockville Centre as bishop of Columbus that same year. Brennan initiated the elevation of Saint Mary of the Assumption in Lancaster to the rank of a minor basilica in August 2019. In December 2020, Brennan announced the "Real Presence Real Future" strategic planning initiative, aiming at "increasing the presence of Christ throughout its 23 counties over the next three years and upholding the Faith for future generations." According to Brennan, the process would likely result in some parishes closing.

In February 2020, the diocese announced the closure of two diocesan retreat centers, St. Therese's in Columbus and Sts. Peter and Paul in Newark. The shuttering was due to dwindling use in part because of more parishes having parish centers, newer non-diocesan facilities being built, and the necessity of repairs at both sites.

• Sts. Peter and Paul was constructed as a seminary for the Pontifical Institute for Foreign Missions in 1957. It closed in 1990, was acquired by the diocese and reopened as a retreat center in 2003. It served as the convent for the Dominican Nuns of the Perpetual Rosary until that community left the diocese in 2023.
• St. Therese Retreat Center opened in 1931. St. Therese now houses the Daughters of Holy Mary of the Heart of Jesus, a group ministering to girls and young women.

Francis appointed Brennan as bishop of the Diocese of Brooklyn in 2021 and then named Reverend Earl K. Fernandes of Cincinnati is the current bishop of Columbus, appointed by Francis in 2022. Fernandes has continued the "Real Presence Real Future" process started by Brennan. In October 2022, the Diocese of Steubenville announced that the Vatican was considering merging that diocese with the Diocese of Columbus. However, facing strong opposition within Steubenville, Bishop Jeffrey Monforton of Steubenville announced a few weeks later that the merger proposal had been put on hold.

In May 2023, the diocese announced that it would closed 15 parishes as part of the “Real Presence, Real Future” initiative. As of 2023, Fernandes is the current bishop of Columbus.

1. Sylvester Horton Rosecrans (1868–1878)
2. John Ambrose Watterson (1880–1899)
3. Henry K. Moeller (1900–1903), later Archbishop of Cincinnati
4. James Joseph Hartley (1903–1944)
5. Michael Joseph Ready (1944–1957)
6. Clarence George Issenmann (1957–1964), later Bishop of Cleveland
7. John Joseph Carberry (1965–1968), later Archbishop of Saint Louis and cardinal
8. Clarence Edward Elwell (1968–1973)
9. Edward John Herrmann (1973–1982)
10. James Anthony Griffin (1983–2004)
11. Frederick Francis Campbell (2005–2019)
12. Robert J. Brennan (2019–2021), later Bishop of Brooklyn
13. Earl K. Fernandes (2022–present)

• Edward Gerard Hettinger (1941–1977)
• George Avis Fulcher (1976–1983), later Bishop of Lafayette in Indiana

• Nicholas Aloysius Gallagher (1846-1916), appointed Bishop of Galveston in 1892
• Francis William Howard, appointed Bishop of Covington in 1923

As of 2020, the Diocese of Columbus comprises 103 parishes and two missions. The parishes are divided into the following deaneries:

The diocese is home to the Museum of Catholic Art and History – the largest institution of its kind in the United States It was founded in 1998 as the Jubilee Museum.

• Mount Carmel College of Nursing – Columbus
• Ohio Dominican University – Columbus
• Pontifical College Josephinum – Columbus (Jurisdiction of the Apostolic Nuncio)

• Bishop Hartley High School – Columbus
• Bishop Ready High School – Columbus
• Bishop Rosecrans High School – Zanesville
• Bishop Watterson High School – Columbus
• Cristo Rey Columbus High School – Columbus
• Newark Catholic High School – Newark
• Notre Dame High School – Portsmouth
• Saint Charles Preparatory School – Columbus
• St. Francis DeSales High School – Columbus
• Tuscarawas Central Catholic High School – New Philadelphia
• William V. Fisher Catholic High School – Lancaster

• Genesis HealthCare System – Zanesville (combination of Good Samaritan Hospital and Bethesda Hospital). Good Samaritan Hospital began in 1900 and is co-sponsored by the Franciscan Sisters of Christian Charity of Manitowoc – Wisconsin.
• Mt. Carmel Hospitals – Columbus (Mt. Carmel – East; Mt. Carmel – West; St. Ann, Westerville). Mt. Carmel opened in 1886, by the Sisters of the Holy Cross from St. Mary's, Indiana. In 1972, Mt. Carmel East opened to serve the suburbs. Also, St. Ann's Hospital was bought by Mt. Carmel in 1995. At one time, St. Ann's was operated by the Sisters of St. Francis of Penance and Christian Charity.
• Trinity Hospital Twin City – Dennison. Bought by the Sisters of St. Francis of Sylvania in May 2011.

Religious Order	Location Served
Apostles of Jesus
Congregation of the Holy Spirit
Congregation of Clerics Regular of the Divine Providence (Theatines)	St. Joseph – Dover Holy Trinity – Zoar Christ the King – Columbus
Fathers of Mercy
Glenmary Home Missioners
Heralds of the Good News	St. John Neumann – Sunbury Church of the Resurrection – New Albany
Institute of Christ the King Sovereign Priest (ICKSP)	St. Leo – Merion Village
Institute of the Incarnate Word
Missionaries of the Precious Blood	St. James the Less – Columbus
Missionary Servants of the Word	St. Stephen the Martyr – Columbus St. Agnes – Columbus
Order of the Blessed Virgin Mary of Mercy (Mercerdarians)	Holy Family – Columbus
Order of Friars Minor
Order of Preachers (Dominicans)	Holy Trinity – Somerset Pontifical College Josephinum Ohio Dominican University St. Joseph – Somerset St. Patrick – Columbus
Society of the Catholic Apostolate (Pallottines)	Sacred Heart – Columbus St. Christopher
Sons of the Immaculate Conception Congregation	Mt. Carmel Hospitals St. Elizabeth – Columbus

• Bridgettine Sisters (Order of the Most Holy Savior) – Holy Family Church – Columbus
• Carmelite Sisters for the Aged and Infirm – Columbus
• Daughters of Holy Mary of the Heart of Jesus
• Dominican Sisters of Mary, Mother of the Eucharist, St. Michael School – Worthington
• Dominican Sisters of Peace – Columbus
• Dominican Sisters of the Immaculate Conception – Columbus
• Franciscan Sisters of Christian Charity – Zanesville
• Franciscan Sisters of the Immaculate Heart of Mary - Our Lady of Peace - Columbus
• Franciscan Sisters of the Immaculate Heart of Mary (from Kerala) – St. Peter – Chillicothe
• Leaven of the Immaculate Heart of Mary – Portsmouth
• Little Servant Sisters of the Immaculate Conception – Columbus, St. John Paul II Education Center
• Salesian Sisters of Don Bosco, St. Francis DeSales High School – Columbus
• Sisters of Charity of Cincinnati – Columbus and Mount Vernon
• Sisters of Notre Dame de Namur – Columbus
• Sisters of the Good Shepherd – Columbus
• Sisters of the Holy Cross – Columbus
• Sisters of St. Francis of Penance and Christian Charity – Columbus
• Third Order of St. Francis (Joliet) – Columbus

There are two stations in the diocese listed below, including:

• WFOT at 89.5 FM licensed to Lexington and serving the Mansfield area. Annunciation Radio airs programming from EWTN Global Catholic Radio. WFOT broadcasts as a simulcast of WNOC.
• WVSG 820 AM Saint Gabriel Radio (the former WOSU (AM))

There are two other stations also reaching the diocese listed below, including:

• WNOP "Sacred Heart Radio" 720 AM licensed to Newport, Kentucky and based in Cincinnati which also airs local and EWTN programming...plus an FM sister, WHSS 89.5 in Hamilton.
• WULM "Radio Maria" 1600 AM in Springfield Radio Maria USA is based at originating station KJMJ 580 AM in Alexandria, Louisiana.

The Catholic Columbian was the first official newspaper of the diocese, created in 1875 by Bishop Sylvester Rosecrans and Father Dennis Clarke. In 1939, the newspaper announced it would no longer associate with the diocese, but continued to publish until 1940, when it was replaced by The Columbus Register. In 1951, the diocese established The Catholic Times, to replace The Columbus Register, it continues publication today.

In 1993, Bishop Griffin removed Reverend Phillip Jacobs from his parish due to allegations that he had sexually abused a teenage boy. The boy's family requested that the police not be notified, but years later Griffin made the notification. When the Diocese of Victoria in British Columbia was considering hiring Jacobs, Griffin informed the diocese about the allegations against him. The Diocese of Victoria hired Jacobs anyway. In 2010, Jacobs was arrested in Victoria, British Columbia for sexual abuse of minors. Jacobs was convicted in 2013 and sentenced to five months of home detention.

In August 2018, Bishop Campbell and the diocese were named in a $2 million lawsuit by Kevin Heidtman, a former student at St. Charles Preparatory School in Columbus. Heidtman alleged that he was sexually molested on at least six occasions at the school by Reverend Thomas Bennett between 2002 and 2003. Bennett died in 2008. The lawsuit alleged that Campbell and the diocese became aware of Bennett's molestation of Heidtman, but failed to take any action."Former St. Charles student files lawsuit, claims he was sexually abused by priest". WCMH News. August 17, 2018. Retrieved August 14, 2024.</ref> After Heidtman filed suit, two other students came forward with accusations again Bennett.

In March 2019, the diocese released a list of 36 clergy with credible accusations of sexual abuse of children, and updated the list to number nearly 50 in September of that year. In August 2020, the diocese paid a $1 million settlement to Heidtman. The diocese had previously resisted calls to release its files of abuse allegations.

Until 2020, the diocese was one of only three dioceses in the nation to have a priest serve as victim assistance coordinator. Victim advocates criticized this practice, saying it can re-traumatize survivors and discourage the reporting of abuse. The diocese hired an outside licensed counselor in July 2020, coinciding with the formation of a Safe Environment Task Force by Bishop Brennan.

• Diocesan website