The Diocese of Davenport (Latin: Diœcesis Davenportensis) is a Latin Church ecclesiastical jurisdiction, or diocese, of the Catholic Church for the southeastern quarter of the state of Iowa in the United States.

The current bishop of Davenport is Dennis Gerard Walsh. The previous bishop, Thomas Zinkula, became Archbishop of Dubuque in 2023. The diocese is a suffragan see of the Archdiocese of Dubuque. The see city for the diocese is Davenport, where Sacred Heart Cathedral is located.

The Diocese of Davenport covers 11,438 square miles (29,620 km).

• The eastern border is the Mississippi River.
• The northern border comprises Jasper, Poweshiek, Iowa, Johnson, Cedar, and Clinton counties.
• The western border comprises Jasper, Marion, Monroe, and Appanoose counties.
• The southern border is the Missouri state line.

From the time of the Louisiana Purchase in 1803 down to 1827, the present day Diocese of Davenport was included in the Diocese of New Orleans. The first Catholic missionaries arrived in the Iowa area during the early 1830s, under the jurisdiction of the Diocese of St. Louis. In 1837, the Vatican erected the Diocese of Dubuque, covering Iowa and adjoining territories.

St. Anthony's Parish in Davenport was established around 1837 by Dominican missionary Samuel Mazzuchelli. Its church was built in 1838 on land donated by French-Potawatomi entrepreneur Antoine Le Claire. The building served as a church, city hall, courthouse, schoolhouse, public forum, and gathering place for the citizens of Davenport.

In 1839, French missionary Jean-Antoine-Marie Pelamourgues was named the first resident pastor of St. Anthony's. His duties included attending the communities of Muscatine, Burlington, Iowa City, Columbus Junction, DeWitt, Lyons, and Stephenson, Illinois, across the Mississippi River from Davenport. Pelamourgues studied to improve his English; when German immigrants began to arrive, he took up that language as well. He helped establish the parish of St. Kunigunda in Davenport, where services were held in Latin and German. When the German pastor at St. Kunigunda refused to serve the needs of Irish immigrants who settled in the west end, Pelamourgues built St. Mary's two blocks away.

Bishop John Hennessy, the third bishop of Dubuque, requested that the Vatican divide Iowa into two dioceses, with the new diocese covering the lower half of the state. Hennessy suggested locating the see of the new diocese in Des Moines, but the Vatican chose Davenport instead.

On May 8, 1881, Pope Leo XIII erected the Diocese of Davenport. He selected Monsignor John McMullen, vicar general of the Archdiocese of Chicago, to serve as the first bishop.

As bishop, McMullen chose St. Margaret's Church in Davenport as the new cathedral. Soon after arriving in Davenport, McMullen went to visit the parishes in his diocese. He traveled the diocese by stagecoach, buggy, lumber wagon, hand car and train. While on visitation, he administered confirmations and other sacraments in many locations.

McMullen called the diocese's first synod in 1882 to set its procedures and regulations. In September 1882, he founded St. Ambrose, a seminary and school of commerce in Davenport. By December 1882, McMullen had confirmed over 13,000 people. After almost two years as bishop, McMullen died in 1883.

Reverend Henry Cosgrove, the diocesan administrator and cathedral rector, was appointed by Leo XIII as the second bishop of Davenport in 1884. Deciding that St. Margaret's was no longer adequate as a cathedral, Cosgrove constructed Sacred Heart Cathedral in 1891 to replace it. He established as Sacred Heart Asylum in Davenport 1895, operated by the Sisters Servants of the Sacred Heart. The Congregation of the Humility of Mary took over the asylum in 1896. Sacred Heart Asylum later became St. Vincent's Home for orphans

Cosgrove supported the national Temperance Movement and called for a moral crusade in the diocese, especially in Davenport. In 1903, he was quoted in the national media as labeling Davenport "the wicked city of its size in America". This was due to the Bucktown District, an area of speakeasies and brothels close to the cathedral.

In 1904, at Cosgrove's request, Pope Pius X named Reverend James J. Davis, vicar general and cathedral rector, as coadjutor bishop of the diocese to assist with its administration. Cosgrove presided over the diocese's second synod the same year. When Cosgrove died in 1906, Davis automatically became bishop of Davenport. At this time, the Vatican started planning for a new diocese in Des Moines. Rather than splitting the Diocese of Davenport into two small dioceses, Davis proposed that Vatican redraw all the diocese boundaries in Iowa. The Archdiocese of Dubuque had 109,000 Catholics and the Diocese of Sioux City had 50,000 Catholics. He opposed the Vatican leaving their boundaries alone while splitting the Diocese of Davenport. Under the existing plan, Davenport would have 35,000 Catholics and Des Moines 25,000 Catholics.

In 1911, Pius X rejected Davis' request and erected the new Diocese of Des Moines from the Diocese of Davenport. However, Pius X did sever Clinton County from the archdiocese and give it to the Diocese of Davenport. This change gave the diocese 50,000 Catholics out of a total population of 589,000.

After Davis died in 1926, Pope Pius XI named Reverend Henry Rohlman of the Archdiocese of Dubuque as the fourth bishop of Davenport. In 1928, Rohlman commissioned a study to assess the social problems in the diocese. The result of this study was the establishment of Catholic Charities in 1929. Its immediate focus was the welfare of the children at St. Vincent's Home in Davenport.

The diocese celebrated its Golden Jubilee in 1931. The next year, Rohlman convoked the diocese's third synod to bring the diocese's regulations in line with the 1917 Code of Canon Law. The synod also set the salary for pastors at $1,000 per year, plus household expenses, and salaries for associate pastors and chaplains at $500. Catholic Charities set up their offices in the Kahl Building. They were joined in 1932 with the chancery and the newly established superintendent of schools. All of these offices and the bishop's office moved into a property on Church Square behind St. Anthony's Church downtown. It was renamed the Cosgrove Building after Bishop Cosgrove. The Catholic Messenger, an independent Catholic newspaper published in Davenport, was experiencing financial problems during the Great Depression; the diocese purchased it in 1937 to use as the diocesan newspaper.

Pope Pius XII named Rohlman as coadjutor archbishop of Dubuque in 1944 and replaced him in Davenport with Bishop Ralph Hayes, rector of the Pontifical North American College in Rome. Catholic school enrollment reached their highest enrollments during Hayes’ episcopate. Elementary school enrollment reached its highest mark in 1960 with 12,074 students and high schools in 1965 with 4,129 students. The National Catholic Welfare Council held a four-day conference in Davenport in 1949, focuring on the themes of industry, education, and rural life. Hayes established the Papal Volunteers of Latin America in the diocese in February 1961 in response to a plea from Pope John XXIII. The diocese sent missionaries to Cuernavaca, Mexico and Ponce, Puerto Rico.

Hayes retired in 1966 after 22 years as bishop of Davenport. To replace him, Pope Paul VI named Auxiliary Bishop Gerald O'Keefe of the Archdiocese of St. Paul. O'Keefe established a sister's council for the members of women's religious orders in 1967 and a lay council in 1970. He created the first diocesan pastoral council and created a diocesan board of education. Procedures for due process were written in the late 1960s. In 1978, O'Keefe established the permanent diaconate in the diocese. The first class of deacons was ordained in 1980. A deacons council was also organized.

O’Keefe joined with Bishops Arthur O'Neil of Rockford and John Franz of Peoria to create an office that assisted migrant workers with job and education services. In 1972, the Social Action department established an Immigration Office. The diocese sent priests to Mexico to learn Spanish and to immerse in its culture. Three Spanish-speaking deacons were ordained in 1981.

The economic recession of the 1980s impacted the diocesan population and resources. In 1991, O'Keefe announced a plan for clustering and closing smaller parishes, reflecting both the reduced number of priests and the lower diocese population. The diocese also witnessed a decline in enrollment in Catholic schools, leading to the merger or closing of schools. In 1970, there were ten hospitals in the diocese; by the time O'Keefe retired in 1993, they were reduced to three.

To replace O'Keefe, Pope John Paul II named Auxiliary Bishop William Franklin of Dubuque as the next bishop of Davenport in 1993. Franklin revised the diocesan staff, creating an Office of Pastoral Services that combined the ministries of liturgy, education, and social action. He replaced the pastoral council with a pastoral council convocation.

In 2000, the diocese celebrated the Jubilee Year proclaimed by John Paul II. There were no diocesan celebrations. Instead, they were planned and celebrated in the diocese's six deaneries. In 2001, the pope bestowed papal honors on 26 people of the diocese. Four priests were named by the Vatican as chaplains to his holiness, eight laymen were honored as knights of St. Gregory the Great, three women received the honor of dames of the Order of St. Gregory the Great, and 11 men and women received the cross oro ecclesia et pontifice. The three women bestowed with the Order of St. Gregory were the first such recipients in the history of the diocese.

Marycrest International University in Davenport, which began as a woman's college in the 1930s, closed in 2002. Mt. St. Clair College in Clinton, Iowa, expanded and became The Franciscan University in 2002 and then the Franciscan University of the Prairies two years later. In 2005, it was sold to Bridgepoint Education, Inc. and became Ashford University, ending its affiliation with the Catholic Church.

Franklin merged or closed several parishes due to changing demographics in the diocese. The Redemptorists, who had served the diocese for 89 years, left in 1997 due to their declining numbers. The Sisters of St. Francis in Clinton built the Canticle, a new motherhouse in Clinton, in 1997. Franklin retired in 2006.

In 2006, Pope Benedict XVI appointed Auxiliary Bishop Martin Amos of the Diocese of Cleveland as the eighth bishop of Davenport. Two days before Amos assumed office, the diocese filed for Chapter 11 Bankruptcy protection. As a result of the bankruptcy, the diocese was forced to sell off property, including the bishop's residence, to pay for a financial settlement to sexual abuse victims. Amos had previously requested a small fixer-upper house to live in, believing the bishop's residence too big for him.

The diocese also sold the chancery building, the St. Vincent Center, and its surrounding property to St. Ambrose University in May 2009. At the same time, the diocese initiated a $22 million capital campaign to replenish diocesan finances and fund other projects. In March 2010, the diocese repurchased St. Vincent Center and 5 acres (2.0 ha) of land from St. Ambrose.

In July 2010, the diocese re-established Catholic Charities. The organization was initially introduced into the diocese in 1929 by Rohlman, but it had been discontinued in 1968. Amos retired in 2017.

Monsignor Thomas Zinkula from Dubuque was appointed bishop of Davenport by Pope Francis in 2017. Zinkula reduced the number of deaneries in the diocese from six to five in 2023. In July 2023, Zinkula was named archbishop of Dubuque. Fr. Dennis G. Walsh was named Bishop of Davenport by Pope Francis on June 25, 2024.

In 1992, Bishop O’Keefe was sued by two women. The plaintiffs claimed that O'Keefe had sexually abused them as young girls when he was rector of St. Paul Cathedral in St. Paul, Minnesota, in the early 1960s. Both women credited recovering repressed memories for their accusations. O'Keefe denied the charges. However, the plaintiffs dropped their lawsuits in 1993 after an investigation revealed that the two women had fabricated the accusations against O'Keefe while together in therapy.

In 2002, Bishop Franklin received allegations of sexual abuse of minors in the 1970s by Reverend William Wiebler. After Wiebler confessed his crimes to Franklin, the bishop ordered him to enter the Vianney Renewal Center, a treatment facility for priests in Dittmer, Missouri. However, Wiebler checked himself out of the facility and never returned to the diocese. The Vatican laicized Wiebler in 2006.

In 2004, the diocese settled the claims of 37 sexual abuse victims for $9 million; Wiebler was named as an abuser in 12 of these lawsuits.

The diocese in October 2006 filed for Chapter 11 protection. By November 2007, the bankruptcy court had allocated $37 million in legal settlements to 156 victims. That same month, Bishop Amos announced that the board of trustees of St. Ambrose University had decided to remove O'Keefe's name from the school library. O'Keefe had covered up sexual abuse crimes by priests in the diocese.

In 2014, documents revealed that Reverend James Janssen, who sexually abused boys and was laicized in 2004, stated in court during lawsuits that "I'm very sick." Janssen died in 2015.

In June 2019, Bishop Zinkula indicated that the diocese would comply with a request from the Iowa Attorney General for sexual abuses records on clerics in the diocese.

In March 2020, the diocese announced that Reverend Robert Grant, a theology professor at St. Ambrose University, had been suspended from teaching and practicing ministry after a sex abuse allegation surfaced. He allegedly committed the sexual abuse while serving in the Diocese of Des Moines in the early 1990s. In November 2020, the diocese announced that Grant was returning to ministry with restrictions. The diocese determined that misconduct had occurred, but that it did not merit a suspension of ministry.

Saint Ambrose in Davenport was founded in 1882 by Bishop McMullen. Located in the school building of St. Margaret's Cathedral, it was then a seminary and commerce school for young men. St. Ambrose moved to its current location in 1885 and became St. Ambrose College in 1908. In 1987, St. Ambrose College became St. Ambrose University.

Since 1947, the diocese has supported the Newman Catholic Student Center at the University of Iowa in Iowa City.

The Congregation of the Humility of Mary founded Visitation Academy in 1864 at their mother house in Ottumwa. The academy underwent several name changes until 1930, when it became Ottumwa Heights College. Ottumwa Heights merged with Indian Hills Community College (IHCC) in 1979 and closed in 1980. IHCC now occupies the Ottumwa Heights campus.

The Congregation of the Humility of Mary founded Marycrest College in Davenport in 1939 as the woman's division of St. Ambrose. It became a separate college in the 1950's and became coeducational in 1969. In 1990, Marycrest was renamed Teikyo Marycrest University and in 1996 as Marycrest International University. Marycrest closed in 2002.

The Sisters of St. Francis of Assisi established Mount St. Claire College for women in 1918 in Clinton. The college began offering online graduate courses in 2002 and changed its name to Franciscan University. In 2004, the school modified its name to Franciscan University of the Prairies. In 2005, the Sisters sold the school to Bridgepoint Education, Inc. which closed it in 2016.