Lucas County is a county located in the northwestern part of the U.S. state of Ohio. It is bordered to the east by Lake Erie, and to the southeast by the Maumee River, which runs to the lake. As of the 2020 census, the population was 431,279. Its county seat and largest city is Toledo, located at the mouth of the Maumee River on the lake. The county was named for Robert Lucas, 12th governor of Ohio, in 1835 during his second term. Its establishment provoked the Toledo War conflict with the Michigan Territory, which claimed some of its area. Lucas County is the central county of the Toledo Metropolitan Statistical Area.

Northwest Ohio, or Northwestern Ohio, consists of multiple counties in the northwestern corner of the US state of Ohio. This area borders Lake Erie, Southeast Michigan, and northeastern Indiana. Some areas are also considered the Black Swamp area. The Toledo metropolitan area is part of the region.