Ohio's 1st congressional district is represented by Democrat Greg Landsman. The district includes the city of Cincinnati, all of Warren County and borders the state of Kentucky. This district was once represented by President William Henry Harrison. After redistricting in 2010, the district was widely seen as heavily gerrymandered by state Republicans to protect the incumbent, Steve Chabot. Chabot lost the seat in 2022 to Landsman, after redistricting unified the city of Cincinnati into the district. The city was previously split between the 1st and 2nd districts.

Warren County is a county located in the southwestern part of the U.S. state of Ohio. As of the 2020 census, the population was 242,337. Its county seat is Lebanon and largest city is Mason. The county is one of Ohio's most affluent, with the highest median income of the state's 88 counties. The county was established on May 1, 1803, from Hamilton County; it is named for Dr. Joseph Warren, a hero of the Revolution who sent Paul Revere and the overlooked William Dawes on their famous rides and who died at the Battle of Bunker Hill. Warren County is part of the Cincinnati, OH-KY-IN Metropolitan Statistical Area.