The Diocese of Youngstown (Latin: Dioecesis Youngstonensis) is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in northeastern Ohio in the United States. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Cincinnati.

The Diocese of Youngstown consists of six counties: Mahoning, Trumbull, Columbiana, Stark, Portage, and Ashtabula. The mother church of the diocese is St. Columba Cathedral in Youngstown.

As of 2020, the Diocese of Youngstown contained 86 parishes with 103 diocesan priests, 13 religious priests, 84 permanent deacons, 26 male religious, and 175 female religious. It had a Catholic population of 163,650 (13.9% of the total population) in an area totaling 3,404 square miles (8,820 km).

As of 2021, the diocese had 15 seminarians studying at the Pontifical College Josephinum in Columbus, Ohio, at St. Vincent Seminary in Latrobe, Pennsylvania, and at St. Mary Seminary in Wickliffe, Ohio.

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, after the end of the French and Indian War, 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 wanted to remove American Catholics from the jurisdiction of their British diocese. He erected the Prefecture Apostolic of the United States in 1784, 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 in 1789 created the Diocese of Baltimore, the first diocese in the United States, to replace the prefecture apostolic.

In 1808, Pope Pius VII erected the Diocese of Bardstown, with jurisdiction over the new state of Ohio along with the other midwest states. Pope Pius VII erected the Diocese of Cincinnati in 1821, taking all of Ohio from Bardstown.Pope Pius IX erected the Diocese of Cleveland in 1847, with territory taken from Cincinnati.

Northeastern Ohio would remain part of the Diocese of Cleveland for the next 97 years. The first Catholic parish in Youngstown, St. Columba, was established in 1847. Its first church was completed in 1850.

One of the earliest Roman Catholic communities in eastern Ohio was in Ashtabula. In 1850, a small group of Catholics in Ashtabula petitioned the Diocese of Cleveland for their own parish. However, the diocese denied the request due to a shortage of clergy. Instead, a visiting priest from Painesville would intermittently undertake a day's journey by horse to Ashtabula over secondary rural roads.

In 1858, the diocese established the St. Joseph Mission in Ashtabula and assigned Father Charles Coquelle as its resident priest. Its original members were primarily Irish and German immigrants, drawn to Ashtabula by the railroad industry. Masses were celebrated in private homes until 1860, when parishioners constructed a small wooden frame church. The purchase of an additional five acres in 1877 allowed construction of St. Joseph's two-story brick secondary school, staffed by the Sisters of the Humility of Mary.

In 1878, a group of Catholics began celebrating mass in a grocery store adjacent to Ashtabula Harbor. Mother of Sorrows Parish was established there in 1890 and a permanent church was constructed in 1898.

Towards the turn of the century, a large influx of Italian Catholics prompted the formation of a third church in Ashtabula. In 1902, parishioners began construction of Our Lady of Mount Carmel Church. The first mass in the new church was celebrated in 1903. As the Catholic presence grew in Ashtabula, parishioners started building a large masonry building to replace the original St. Joseph's Church in 1905. That church cost $34,000 to build.

Another early settlement of Catholics was in Dungannon. The mission was first settled on St. Paul's Street. The original log cabin is standing today.

Pope Pius XII erected the Diocese of Youngstown with territory from Diocese of Cleveland in 1943. The new diocese included the counties of Ashtabula, Columbiana, Mahoning, Portage, Stark, and Trumbull. The pope named Auxiliary Bishop James A. McFadden of the Diocese of Cleveland as the first bishop of Youngstown. St. Columba Church in Youngstown became the cathedral for the diocese.

The Diocese of Youngstown covered 3,404 square miles (8,820 km) with 110 parishes, three Catholic-run hospitals, 54 elementary schools, one junior high school, and three Catholic high schools.

In 1949, Pius XII appointed Bishop Emmet M. Walsh of the Diocese of Charleston as a coadjutor bishop to assist McFadden. After McFadden died in 1952, Walsh succeeded automatically succeeded him as bishop. In 1954, St. Columba Cathedral was destroyed by a fire; Walsh immediately started planning a new cathedral. St. Patrick Church in Youngstown served as the pro-cathedral until the new St. Columba's was dedicated in 1958. In 1960, Pope John XXIII named Reverend James Malone as an auxiliary bishop for the diocese. Walsh College was founded in North Canton in 1960 by the Brothers of Christian Instruction. After Walsh died in 1968, Pope Paul VI appointed Malone as bishop that same year.

The closing of Youngstown Sheet and Tube in 1977 resulted in 5,000 workers from the Youngstown area losing their jobs. Malone had led an unsuccessful effort by clergy from different faiths to stop the closing. A strong advocate of interfaith communication, Malone was elected as the first Catholic leader of the Ohio Council of Churches. He delivered sermons in Protestant churches and urged his priests to establish contacts with non-Catholic congregations. Malone retired in 1996 after 28 years as bishop of Youngstown. Pope John Paul II appointed Auxiliary Bishop Thomas J. Tobin from the Diocese of Pittsburgh as the fourth bishop of Youngstown in 1996.

In 2005, John Paul II appointed Tobin as bishop of the Diocese of Providence. The post of bishop remained vacant for almost two years, with Monsignor Robert J. Siffrin serving as diocesan administrator. In 2007, Pope Benedict XVI named Bishop George Murry of the Diocese of St. Thomas as the fifth bishop of Youngstown. In 2010, Murry announced the reconfiguration of parishes in the diocese to reduce their total number to 87.

In May 2020, Murry died of leukemia. Siffrin served again as diocesan administrator from June 2020 to January 2021. During the absence of a bishop, Bishop Emeritus Martin J. Amos of the Diocese of Davenport performed ordinations for the diocese. In November 2020, Pope Francis named Reverend David J. Bonnar of Pittsburgh as the sixth bishop of Youngstown.

From 2000 to 2018, baptisms fell by 69%, weddings by 62%, first communions by 61%, and funerals by 25% in the diocese. The Catholic population fell by 36%, compared with a total population decrease of 4.3%. As of 2023, Bonnar is the bishop of Youngstown.

In 2013, the diocese settled 11 sexual abuse lawsuits brought by former high school students in Warren who had been sexually abused by Brother Stephen Baker, a Franciscan friar. Serving as a baseball coach at John F. Kennedy High School, he abused teenage boys under the pretense of providing athletic massages. When the settlement was announced, Baker committed suicide at his monastery in Pennsylvania. In September 2016, the Diocese of Youngstown and Baker's former religious order were ordered to pay $900,000 to settle 28 more claims of sexual abuse by him.

In October 2018, the Diocese of Youngstown released a list of over 30 priests and other clergy with credible accusations of sexual abuse of minors

Reverend Denis G. Bouchard, former pastor of Queen of the Holy Rosary Parish in Vienna, sued the diocese and three individuals who had accused him of child sexual abuse in October 2019. He had been on administrative leave since the accusations arose in November 2018. William Smalz, a former priest, filed a defamation lawsuit against the diocese in October 2020. When the diocese published their list of accused priests in 2018, they included Smalz on the list. The diocese removed his name in May 2020, saying that new information had proved the allegations against Smalz were not credible.

In April 2023, the Maryland District Attorney released an investigative report on sexual abuse by priests in that state. The report related the history of Reverend John Hammer, who served in Youngstown and East Liverpool during the early 1980s. The diocese had sent him to a facility in Maryland in 1985 for treatment of sex addiction and pedophilia. After his treatment, Bishop Malone said that Hammer could not return to Youngstown. After serving as chaplain at St. Agnes Hospital in Baltimore for several years, Hammer was allowed to serve in a parish in Michigan. Hammer was accused of abusing a child in Michigan. In 2002, three former altar boys sued the diocese, saying that it knew about Hammer's problems, but kept him in ministry. Hammer was removed from ministry in 2002.

1. James A. McFadden (1943–1952)
2. Emmet M. Walsh (1952–1968; Coadjutor 1949–1952)
3. James W. Malone (1968–1995)
4. Thomas J. Tobin (1995–2005), appointed Bishop of Providence
5. George V. Murry (2007–2020)
6. David Bonnar (2021–present)

• James W. Malone (1960–1968), appointed Bishop of Youngstown
• William A. Hughes (1974–1979), appointed Bishop of Covington
• Benedict C. Franzetta (1980–1996)

• Early Childhood Learning Center at Holy Family – Poland
• Early Childhood Learning Center at St. Charles – Boardman
• Early Childhood Learning Center at St. Christine – Youngstown
• Early Childhood Learning Center at St. Joseph – Austintown
• Early Childhood Learning Center at St. Luke – Boardman
• Holy Family School – Poland
• Saint Charles School – Boardman
• Saint Christine School – Youngstown
• St. Joseph – Mogadore
• St. Jude School – Columbiana
• Saint Nicholas School – Struthers
• Saint Rose School – Girard

• Cardinal Mooney High School – Youngstown
• John F. Kennedy High School – Warren (Upper Campus)
• St. Thomas Aquinas High School – Louisville
• Ursuline High School – Youngstown

Most of the Catholic elementary/middle schools within Stark County are part of Stark County Catholic Schools, formerly known as Holy Cross Academy. As of 2023, the system has the following campuses:

• Our Lady of Peace – Canton
• Regina Coeli – Alliance
• St. Barbara – Massillon
• St. James – Waynesburg
• St. Joan of Arc – Canton
• St Mary – Massillon
• St Michael the Archangel – Canton
• St Paul – North Canton
• St Peter – Canton
• Sts Philip and James – Canal Fulton
• St. Thomas Aquinas Middle School – Louisville
• Central Catholic High School – Canton

• John F. Kennedy Catholic School – Warren. The lower campus was named Notre Dame School: Blessed Sacrament Campus until 2010.
• Saint John High School* – Ashtabula
• Saint John School – Ashtabula
• Saint Joseph School – Randolph
• Saint Joseph the Provider School – Youngstown
• Saint Patrick School – Kent
• Saint Paul School – Salem
• Saint Rose School – Girard
• Ursuline Preschool and Kindergarten – Youngstown
• Villa Maria Teresa Preschool and Kindergarten – Hubbard

• Assumption School – Geneva (closed 2015)
• Byzantine Catholic Central School – Youngstown (closed 2009)
• Holy Cross Academy at Saint Joseph Canton Campus – Canton (closed 2014)
• Holy Trinity School - Struthers, Ohio/Mahoning (closed 1992)
• Immaculate Conception School – Ravenna (closed 2004)
• Mother of Sorrows School – Ashtabula (merged with St. John School)
• Notre Dame School – Saint Pius X Campus – Warren (closed 2010 )
• Our Lady of Mount Carmel School – Ashtabula (Merged with St. John School)
• Sacred Heart of Mary School – Harrisburg/Louisville (closed 2009)
• Saint Aloysius School – East Liverpool (closed 2015)
• Saint Anthony School – Canton (closed 1980s)
• Saint Clement School – Navarre (closed 2008)
• Saint Frances Cabrini School – Conneaut (closed 2002)
• Saint John the Baptist School – Canton (closed 1982)
• Saint Joseph and Immaculate Heart of Mary School – Austintown (closed 2014)
• St. Joseph School – Ashtabula (closed 1980s)
• Saint Joseph Mantua School – Mantua (closed 2010)
• Saint Louis – Louisville (closed 2019)
• Saint Mary's of the Immaculate Conception School – Canton (closed 1985)
• Saint Matthias School – Youngstown (closed 2006)
• Saint Mary School – Conneaut (closed 1972 – merged with St. Frances Cabrini School)
• Saints Mary and Joseph School – Newton Falls (closed 2011)
• Saint Patrick School – Hubbard (closed 2016)

Walsh University – North Canton

• Kent State University Parish Newman Center – Kent
• Youngstown State University Newman Center – Youngstown

• WILB The Living Bread Radio Network

The Diocese of Youngstown for 78 years published a print newspaper, The Catholic Exponent. Started in 1944, the Exponent was replaced in 2023 by the Catholic Echo, a magazine published 10 times a year.

• Official Website
• Vocations website
• Faith and Family Festival website