The Diocese of Des Moines (Latin: Diœcesis Desmoinensis) is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in southwestern Iowa in the United States. It is a suffragan see in the ecclesiastical province of the metropolitan Archdiocese of Dubuque. The see city for the diocese is Des Moines. The cathedral parish for the diocese is St. Ambrose.

As of 2024, William Joensen is bishop of the Diocese of Des Moines.

Like other American dioceses, the area that makes up the present diocese was under the jurisdiction of a number of prelates. Most of these were purely academic because of no actual Catholic presence in the area. The first Catholic missionaries arrived in the Iowa area during the early 1830s. They were under the jurisdiction of the bishop of Saint Louis, Joseph Rosati.

In 1838, Pope Gregory XVI erected the new Diocese of Dubuque. This diocese initially included all of Iowa as well as a large part of the western United States. By 1850, the diocese only included the state of Iowa. The first mass in what would become the city of Des Moines was celebrated in a log hut in 1851 at Fort Des Moines by Father Alexander Hattenberger, a priest from Ottumwa, Iowa. In 1856, the first St. Ambrose Church was built in Des Moines..

In the late 19th century, Bishop John Hennessy of Dubuque petitioned the Vatican to create a separate diocese for southern Iowa. While he envisioned Des Moines as the see city for this new diocese, in 1881 the Vatican instead erected the Diocese of Davenport, including the Des Moines area.

On August 12, 1911, Pope Pius X erected the new Diocese of Des Moines with territory from the Diocese of Davenport. Saint Ambrose Parish church became the cathedral for the new diocese. The pope in 1912 appointed Austin Dowling of the Diocese of Providence as the first bishop of Des Moines. In 1918, Dowling founded Des Moines Catholic College. A year later, Pope Benedict XV named Dowling as archbishop of the Archdiocese of St. Paul.

To replace Dowling in Des Moines, Benedict XV named Thomas Drumm in 1919. Drumm died in 1933. In 1934, Gerald Bergan of the Diocese of Peoria was appointed the third bishop of Des Moines by Pope Pius XI. He established a diocesan newspaper called The Messenger. Pope Pius XII named Bergan as archbishop of the Archdiocese of Omaha in 1948. Bergan's replacement in Des Moines was Edward Daly, named by the pope that same year. Daly died in 1964.

Auxiliary Bishop George Biskup of the Archdiocese of Dubuque was named by Pope Paul VI as the fifth bishop of Des Moines in 1965. In 1966, he purchased 55 acres (220,000 m) from the Des Moines Golf and Country Club in West Des Moines to construct Dowling Catholic High School. He also started to implement the changes in the church as a result of the Second Vatican Council reforms.

In 1967, after Biskup was in Des Moines for only two years, Paul VI appointed him as coadjutor archbishop for the Archdiocese of Indianapolis. In 1968, the pope named Maurice Dingman of the Diocese of Davenport as the next bishop of Des Moines. In 1979, while on his American tour, Pope John Paul II visited the diocese on the suggestion of Joe Hays, a farmer in Truro and on the invitation of Dingman. After arriving in Des Moines, the pope visited St. Patrick Parish near Irish Settlement. He then celebrated a mass at the Living History Farms in Urbandale before leaving Iowa. Dingman retired due to bad health in 1986.

In 1987, John Paul II replaced Dingman as bishop of Des Moines with Auxiliary Bishop William Bullock from the Archdiocese of Saint Paul and Minneapolis. In 1993, the pope named him as bishop of the Diocese of Madison. The new bishop of Des Moines was Auxiliary Bishop Joseph Charron from Saint Paul and Minneapolis, named by the pope in 1994. Charron retired in 2007.

In 2008, Pope Benedict XVI appointed Auxiliary Bishop Richard Pates from Saint Paul and Minneapolis as the ninth bishop of Des Moines. In 2010, the diocese was the victim of a cybercrime, losing $600,000 in the attack by a criminal gang in a foreign country. The Federal Bureau of Investigation ultimately recovered $180,000 for the diocese. Pates resigned in 2018.

Pope Francis in 2019 named William Joensen from the Archdiocese of Dubuque as the next bishop of Des Moines. In January 2023, the diocese released new restrictive policies on the treatment of transgender individuals in diocesan churches, schools and other facilities.

As of 2023, Joensen is the bishop of Des Moines.

In 2003, Bishop Charron permanently suspended three diocesan priests from ministry due to sexual abuse allegations: Albert Wilwerding, John Ryan, and Richard Wagner. Charron was following the recommendations of an internal committee that had recommended their dismissal and laicization.

In 2015, Pope Francis laicized Reverend Howard Fitzgerald, who was credibly accused of sexually abusing a minor in the previous decades. Fitzgerald had been placed on administrative leave in 2014. In April 2019, Bishop Pates released a list of nine diocesan priests with credible accusations of sexual abuse of minors.

In March 2020, the diocese announced that it was suspending Reverend Robert Grant, a professor at St. Ambrose University in Davenport, from teaching and practicing ministry after a sex abuse allegation surfaced. Grant allegedly committed the abuse while working at St. Albert High School in Council Bluffs in the early 1990s. After the accuser reached out to sex abuse advocates, they reported the allegations to the diocese. However, the statute of limitations in Iowa prevented the accuser from pursuing criminal charges against Grant. In November 2020, the diocese determined that Grant's sexual misconduct took place when the accuser was above the age of consent. Therefore, the diocese returned Grant to his ministry and teaching positions with restrictions.

1. Austin Dowling (1912–1919), appointed Archbishop of Saint Paul
2. Thomas William Drumm (1919–1933)
3. Gerald Thomas Bergan (1934–1948), appointed Archbishop of Omaha
4. Edward Celestin Daly (1948–1964)
5. George Biskup (1965–1967), appointed Coadjutor Archbishop and later Archbishop of Indianapolis
6. Maurice John Dingman (1968–1986)
7. William Henry Bullock (1987–1993), appointed Bishop of Madison
8. Joseph Charron (1993–2007)
9. Richard Pates (2008–2019)
10. William Michael Joensen (2019–present)

John Joseph Boylan, appointed Bishop of Rockford in 1942

School	Location	Mascot
Dowling Catholic High School	West Des Moines	Maroons
Saint Albert High School	Council Bluffs	Falcons

School	Location	Mascot	Fate
Assumption	Granger	Tigers	Absorbed by Dowling Catholic, West Des Moines, in 1966
St. Boniface	Westphalia	Trotters	Merged with St. Paul's, Defiance, becoming SS Peter and Paul, Defiance in 1964
St. Joseph's	Dunlap	Shamrocks/Royals	Closed in 1961
St. Joseph's	Earling	Eagles	Closed in 1967
St. Joseph's	Neola	Rockets	Consolidated with St. Francis, Council Bluffs, to form St. Albert's, Council Bluffs in 1964
St. Mary's, Panama-Portsmouth	Portsmouth	Knights	Closed in 1967
St. Patrick Academy	Imogene	Shamrocks	Closed in 1969
St. Patrick's	Perry	Knights	Closed in 1966
SS Peter and Paul	Defiance	Trojans	Closed in 1967

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