The Roman Catholic Archdiocese of Cincinnati (Latin: Archidioecesis Cincinnatensis) covers the southwest region of the U.S. state of Ohio, including the greater Cincinnati and Dayton metropolitan areas. The Archbishop of Cincinnati is Most Rev. Dennis Marion Schnurr.

In total, the Archdiocese of Cincinnati encompasses 230 parishes in 19 counties, as of 2005^[update], with the total membership of baptized Catholics around 500,000. The Archdiocese administers 110 associated parochial schools and diocesan elementary schools. Its mother church is the Cathedral of St. Peter in Chains; located at the corner of 8th and Plum Streets in Downtown Cincinnati.

Cincinnati is the metropolis of the Ecclesiastical Province of Cincinnati, which encompasses the entire state of Ohio and is composed of the Archdiocese and its five suffragan dioceses: Cleveland, Columbus, Steubenville, Toledo, and Youngstown.

The Archdiocese of Cincinnati is bordered by the Diocese of Toledo to the north, the Diocese of Columbus to the east, the Diocese of Covington to the south, and the Archdiocese of Indianapolis and Diocese of Lafayette to the west.

Cincinnati (pronounced /sɪnsɨˈnæti/) is a city in and the county seat of Hamilton County, Ohio, United States. Settled in 1788, the city is located north of the Ohio River at the Ohio-Kentucky border, near Indiana. The population within city limits was 296,943 according to the 2010 census, making it Ohio's third-largest city. According to the 2011 Census Bureau estimate, the Cincinnati metropolitan area had a population of 2,138,038, the 27th most populous Metropolitan Statistical Area (MSA) in the United States, and the most populous in Ohio. Residents of Cincinnati are called Cincinnatians.

In the early 19th century, Cincinnati was the first American boomtown in the heart of the country to rival the larger coastal cities in size and wealth. As the first major inland city in the country, it is sometimes thought of as the first purely American city. It developed initially without as much recent European immigration or influence as took place in eastern cities. However, by the end of the 19th century, with the shift from steamboats to railroads, Cincinnati's growth had slowed considerably and the city became surpassed in population and prominence by another inland city, Chicago.