The Diocese of Rockford (Latin: Diœcesis Rockfordiensis) is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in Northern Illinois in the United States. It is a suffragan diocese of the metropolitan Archdiocese of Chicago.

The mother church of the Diocese of Rockford is the Cathedral of Saint Peter in the City of Rockford. Pope Benedict XVI appointed David Malloy as the ninth and current bishop on March 20, 2012.

The Diocese of Rockford comprises the counties of Boone, Carroll, DeKalb, Jo Daviess, Kane, Lee, McHenry, Ogle, Stephenson, Whiteside and Winnebago.

During the 17th century, present day Illinois was part of the French colony of New France. The Diocese of Quebec, which had jurisdiction over the colony, sent numerous French missionaries to the region. It was estimated that 15,000 to 20,000 Native American converts and French trappers and settlers throughout the region were tended to by these Jesuit missionaries.

After the British took control of New France in 1763, the Archdiocese of Quebec retained jurisdiction in the Illinois area. However, most of the French Catholics in the area migrated to Louisiana.

In 1776, the new United States claimed sovereignty over the area of Illinois. 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 1785, the vicar apostolic, John Carroll, sent his first missionary to Illinois. In 1787, the Illinois 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.

When the Vatican erected the Diocese of Bardstown in Kentucky in 1808, it gained jurisdiction over the Illinois area. The jurisdiction over northern Illinois shifted in 1834 to the Diocese of St. Louis. The first Catholic mass in Elgin was conducted by two French missionaries in 1837.

With the creation of the Diocese of Chicago in 1843, northern Illinois was transferred from the Diocese of St. Louis. The Rockford area would be part of the Diocese of Chicago, followed by the Archdiocese of Chicago, for the next 64 years.

In Elgin, the first Catholic church, St. Mary's, opened in 1851. That same year, Bishop James Van de Velde of Chicago purchased land for the first Catholic church in Aurora. The first Catholic church in Rockford was St. James, founded in 1853. The first parochial school in the city was started in 1855.

Pope Pius X erected the Diocese of Rockford on September 27, 1907. Its territory of 12 counties was taken from the Archdiocese of Chicago. The pope appointed Auxiliary Bishop Peter Muldoon of Chicago as the first bishop of Rockford. With the 1917 entry of the United States into World War I, Muldoon ministered to soldiers and recruits at Camp Grant, the US Army facility in Rockford. He died in 1927.

Auxiliary Bishop Edward Hoban of Chicago was named by Pope Pius XI in 1928 as bishop of Rockford. During his tenure, Hoban opened many elementary and high schools in the diocese, modernized charitable institutions, and established a diocesan newspaper. In 1942, Pope Pius XII appointed Hoban as coadjutor bishop for the Diocese of Cleveland.

The next bishop of Rockford was Monsignor John Boylan from the Diocese of Des Moines, appointed by Pius XII in 1942. During his tenure as bishop, Boylan was able to reduce the diocese's debt while adding new parishes and schools to meet population growth. In 1948, Pope Pius XII established the Diocese of Joliet and transferred Kendall County, Illinois, from Rockford to Joliet. After Boylan died in 1953, Pius XII named Reverend Raymond Hillinger from Chicago to replace him that same year. Three years later, Pius XII appointed Hillinger as an auxiliary bishop in Chicago.

Auxiliary Bishop Loras Lane from the Archdiocese of Dubuque replaced Hillinger in 1956, appointed by Pius XII. Lane died in 1968, leaving Pope Paul VI to name Arthur O'Neill from the Diocese of Providence to take Lane's place.

In 1992, Reverend William Joffe, a diocesan priest, pleaded guilty to two counts of bank fraud and one count of interstate transportation of a fraudulent check and received one year in prison. He also embezzled $265,000 from his parish in McHenry County. He spent the money on a horse farm in Harvard, Illinois, and a resort and restaurant in Wisconsin. After his release from prison in 1992, Joffe was assigned to a new parish. However, after only a few months, Joffe was suspended from the priesthood in 1993.

Serving as bishop of Rockford for 26 years, O'Neill retired in 1994. Pope John Paul II selected Reverend Thomas G. Doran the next bishop of Rockford. Doran retired in 2012. As of 2023, the current bishop of Rockford is David Malloy, appointed by Pope Benedict XVI in 2012.

1. Peter Muldoon (1908-1927)
2. Edward Francis Hoban (1928-1942), appointed Coadjutor Bishop and later Bishop of Cleveland
3. John Joseph Boylan (1942-1953)
4. Raymond Peter Hillinger (1953-1956), appointed Auxiliary Bishop of Chicago
5. Loras Thomas Lane (1956-1968)
6. Arthur Joseph O'Neill (1968-1994)
7. Thomas George Doran (1994-2012)
8. David John Malloy (2012–present)

• Leo Binz, appointed Coadjutor Bishop in 1942 and later Bishop of Winona, Coadjutor Archbishop and later Archbishop of Dubuque, and Archbishop of Saint Paul and Minneapolis
• Timothy Lawrence Doherty, appointed Bishop of Lafayette in Indiana in 2010
• David Kagan, appointed Bishop of Bismarck in 2011

• Aquin Catholic Schools (Junior-Senior High Campus) – Freeport
• Aurora Central Catholic High School – Aurora
• Boylan Catholic High School – Rockford
• Marian Central Catholic High School – Woodstock
• Marmion Academy – Aurora
• Newman Central Catholic High School – Sterling
• Rosary High School – Aurora
• St. Edward Central Catholic High School – Elgin

In 1993, soon after William Joffe was released from prison, a man reported that he had been sexually abused by Joffe in the early 1970's. In 2004, the diocese announced that it had received four allegations from men who said they had been sexually abused by Joffe during the 1970's and early 1980's. After the announcement, five more victims of Joffe came forward. In 2006, Andrew Howell, a Colorado man sued the diocese, claiming he had been abused by Joffe when he was eight years old at St. Mary Parish in Woodstock in the late 1970's. Joffe had already been suspended from ministry in 1993.

In 2002, after the story appeared in the media, Bishop Doran confirmed that Reverend Harlan Clapsaddle, a diocese priest, had sexually abused three brothers when they were children during the 1970s. When the boys complained about him in 1996 to the diocese, it removed Clapsaddle immediately after an investigation. The family said they urged Doran to report Clapsaddle to the police and search for other victims, but he instead told them to stay silent about it. The brothers each received a $27,000 cash settlement in 1997. After sending Clapsaddle away for treatment, the diocese re-assigned him to a nursing home on his return. Clapsaddle was permanently removed from ministry in 2002.

Reverend Mark Campobello pleaded guilty in 2004 to two counts of aggravated criminal sexual abuse. Two women had accused him of indecent touching when they 14 and 15 years old in 1999 and 2000. He was sentenced to eight years in prison. The Vatican laicized Campobello in 2005. The two victims sued the diocese in 2004; they reached a $2.2 million settlement with the diocese in 2007.

In November 2018, Bishop Malloy released a list of 15 clerics, including one deacon and one brother, from the diocese who had been accused of acts of sexual abuse from 1925 to 1991.

In March 2019, Malloy revoked the priestly faculties of Reverend Joseph Jablonski, a priest of the Missionaries of the Sacred Heart who served in for a period in Aurora during the early 2010's. While ministering in the Diocese of San Bernardino in California in 2014, Jablonski allegedly made remarks to a young boy that constituted sexual grooming. When the Diocese of San Bernardino learned of the incident in 2018, it immediately reported him to authorities and banned him from ministering in that diocese.

On May 23, 2023, the Illinois Attorney General released a report on Catholic clergy child sex abuse in Illinois. The multi-year investigation found that more than 450 Catholic clergy in Illinois abused nearly 2,000 children since 1950.

On September 30, 2000, John Earl, a Rockford Catholic priest, drove his car into the Northern Illinois Health Clinic after learning that the FDA had approved the drug RU-486. He pulled out an ax before being forced to the ground by the owner of the building, who fired two warning shots from a shotgun. He was sentenced to 30 months of probation and paid over $7,000 in fines and restitution, but was not removed from the priesthood.

• Kagan, David; Easton, Laurine M. (2007). History of the Diocese of Rockford. Strasbourg, France: Éditions du Signe. ISBN 978-2-7468-1816-3.

• Roman Catholic Diocese of Rockford Official Site
• Catholic Hierarchy