The Diocese of Tyler (Latin: Dioecesis Tylerensis) is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in eastern Texas in the United States. The episcopal see is Tyler, and the Cathedral of the Immaculate Conception in Tyler is its mother church.

The Diocese of Tyler is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Galveston-Houston.

The first Catholic mission in Texas, then part of the Spanish Empire, was San Francisco de los Tejas. It was founded by Franciscan Father Damián Massanet in 1690 in the Weches area. The priests left the mission after three years, then established a second mission, Nuestro Padre San Francisco de los Tejas. near present-day Alto in 1716.

In 1839, three years after the founding of the Republic of Texas, Pope Gregory XVI erected the prefecture apostolic of Texas, largely covering the territory of the present American State of Texas. By the 1840s, missionaries were visiting Clarksville and Nacogdoches. The prefecture was elevated to a vicariate apostolic in 1842, about three years before Texas became an American state. On May 4, 1847, Pope Pius IX elevated the vicariate into the Diocese of Galveston. Marshall received its first missionary visit in 1853. The Tyler area would remain part of several Texas dioceses for the next 139 years.

Pope John Paul II founded the Diocese of Tyler on December 12, 1986, and it was formally erected on February 24, 1987. He appointed Charles Herzig of the Diocese of Galveston-Houston as its first bishop. Herzig died in 1991. In 1992, John Paul II appointed Auxiliary Bishop Edmond Carmody as bishop of Tyler. The pope named Carmody as bishop of the Diocese of Corpus Christi in 2000.

Auxiliary Bishop Álvaro Corrada del Río from the Archdiocese of Washington was named bishop of Tyler by John Paul II in 2001. Pope Benedict XVI appointed del Rio as bishop of the Diocese of Mayagüez in 2011.

Joseph Strickland of the Diocese of Dallas was named bishop of Tyler by Benedict XVI in 2011. Strickland was the first native East Texan to head the diocese.

In June 2023, it was revealed that the Dicastery for Bishops in Rome had completed an apostolic visitation to the diocese. It was conducted by Bishop Emeritus Gerald Kicanas and Bishop Dennis Sullivan. Visitations are frequently a prelude to disciplinary action by the Vatican against a bishop.

Pope Francis relieved Bishop Strickland from the pastoral governance of the diocese on November 11, 2023. The rare removal occurred two months following news that, following the apostolic visitation, several senior cardinals had advised Pope Francis to place pressure on Strickland to resign. In May 2023, Strickland had posted online "I reject [Pope Francis's] program of undermining the Deposit of Faith".

Gustavo Cuello was arrested in 1997 on charges of raping a 13-year-old altar girl. The victim said that he attacked her once or twice a week for six months. After posting bail, Cuello fled to his native Ecuador. In 2003, Ecuador extradited him back to the United States. At trial, Cuello pleaded guilty and was sentenced to life in prison. The Vatican laicized him in 2006.

In February 2019, the diocese published the names of three priests associated with the diocese who had been credibly accused of sexually abusing minors. Only one of the three, Cuello, had allegations reported within the diocese.

1. Charles Edwin Herzig (1986–1991), died in office
2. Edmond Carmody (1992–2000), appointed Bishop of Corpus Christi
3. Álvaro Corrada del Río (2000–2011), appointed Bishop of Mayagüez in Puerto Rico
4. Joseph E. Strickland (2012–2023), removed by Pope Francis

• Joe S. Vásquez, as apostolic administrator (2023–present)

• Eduardo Alanis Nevares, appointed Auxiliary Bishop of Phoenix in 2010

The Diocese of Tyler comprises the following 33 counties in east and northeast Texas:

Anderson, Angelina, Bowie, Camp, Cass, Cherokee, Delta, Franklin, Freestone, Gregg, Harrison, Henderson, Hopkins, Houston, Lamar, Leon, Madison, Marion, Morris, Nacogdoches, Panola, Rains, Red River, Rusk, Sabine, San Augustine, Shelby, Smith, Titus, Trinity, Upshur, Van Zandt, and Wood.

The parishes are grouped into seven deaneries for administrative purposes: Northwest, Northeast, West Central, Central, East Central, Southwest, and Southeast.

• Bishop T. K. Gorman High School, Tyler
• St. Mary's Catholic School, Longview
• St. Boniface Catholic Classical High School, Nacogdoches

• Roman Catholic Diocese of Tyler official site

32°20′03″N 95°18′00″W / 32.33417°N 95.30000°W / 32.33417; -95.30000