The Diocese of Lexington () is a Roman Catholic diocese in southeastern Kentucky in the United States. Erected in 1988, it is a suffragan of the metropolitan Archdiocese of Louisville.
The first Catholic immigrants to the Kentucky area came from Maryland in 1785. By 1796, approximately 300 Catholic families were living in the new state of Kentucky. Among the early missionaries was Stephen Badin, who set out on foot for Kentucky on in 1793, sent by Bishop John Carroll of the Diocese of Baltimore. For the next 14 years Badin traveled on foot, horseback and boat between widely scattered Catholic settlements in Kentucky and the Northwest Territory. For three years, Badin was the only priest in the whole of Kentucky.
In 1808, Pope Pius VII erected the Diocese of Bardstown, covering Kentucky and most of the Northwest Territory. Saint Paul, the first Catholic church in Lexington, was constructed in 1813.
In 1841, Pope Leo suppressed the Diocese of Bardstown, which by this time encompassed only Kentucky. In its place, he created the Diocese of Louisville, with jurisdiction over the entire state. The Diocese of Covington was erected in 1853, consisting of most of the counties that today represent the Diocese of Lexington. The Lexington area remained part of these two dioceses for the next 135 years. St. Joseph Hospital, the first hospital in Lexington, opened in 1877.
Pope John Paul II established the Diocese of Lexington on January 14, 1988. The new diocese would include 43 counties from the Diocese of Covington and seven counties from the Archdiocese of Louisville.
John Paul II named Auxiliary Bishop James Williams of Covington as the first bishop of Lexington. Christ the King Church was elevated to the status of cathedral.
In early 2002, Williams went on leave as bishop of Lexington after sexual abuse allegations arose from his service with the Archdiocese of Louisville. He resigned as bishop of Lexington in July 2002. Ronald Gainer replaced Williams. In 2014, Gainer was made bishop of the Diocese of Harrisburg.
As of 2023, the bishop of the Diocese of Lexington is John Stowe, named by Francis in 2015.
The diocese was sued in August 2016 by three former students at Lexington Catholic High School in Lexington. One male plaintiff said he was physically assaulted at the school, a female plaintiff stated she was a victim of sexual harassment and sex discrimination, and a second male said he experienced racial discrimination.
In May 2024, Christian Matson, a hermit and Benedictine oblate employed by the diocese, came out publicly as transgender. He is believed to be the first hermit of the Catholic Church to do so.
Police arrested Leonard B. Nienaber in April 1993 on charges on sexual abuse and indecent or immoral practices with others. The nine complainants accused the priest of abusing them as minors between 1962 and 1978 when he was pastor of Mary Queen of the Holy Rosary Parish in Lexington. Nienaber pleaded guilty to ten counts of child molestation in 1994, received a ten-year suspended sentence, and was remanded to live at a church facility in Missouri for the rest of his life.
In August 2020, the diocese released a list of 20 priests with different levels of accusations of sexual abuse. Bishop Stowe wrote that ten of the allegations were "substantiated," four allegations were deemed "credible," and the remaining six allegations were "credible" but involved minors living outside the diocese. All except two allegations were for incidents that occurred before the diocese was erected in 1988.