The Cincinnati Reds are a Major League Baseball team based in Cincinnati, Ohio. They are members of the National League Central Division. The club, following illegitimate expulsion from the National League in 1880, was re-established in the following season as a charter member of the American Association in 1882. Cincinnati would go on to (re)join the National League in 1890.

The Reds have won five World Series titles, one American Association pennant, nine National League pennants and nine division titles. The Reds played in the National League West between 1969 and 1993 and since 1994 in the National League Central.

Since 2003, the Reds have played at Great American Ball Park, built next to their home from 1970, Riverfront Stadium. Bob Castellini has owned the Cincinnati Reds since 2006.

The origins of the modern Cincinnati Reds can be traced to the unlawful expulsion of an earlier Reds team. In 1876, Cincinnati became one of the charter members of the new National League, but the club ran afoul of league organizer and long-time president William Hulbert for selling beer at the ballpark and playing games on Sunday, both important activities to entice the city's large German population. While Hulbert made clear his distaste for both beer and Sunday baseball at the founding of the league, neither practice was actually against league rules in those early years. On October 6, 1880, however, seven of the eight team owners pledged at a special league meeting to formally ban both beer and Sunday baseball at the regular league meeting that December. Only Cincinnati president W.H. Kennett refused to sign the pledge, so the other owners illegally banned Cincinnati for 'violating' a rule that would not actually go into effect for two more months.

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.