Defiance is a city in and the county seat of Defiance County, Ohio, United States, about 55 miles southwest of Toledo and 47 miles northeast o…Defiance is a city in and the county seat of Defiance County, Ohio, United States, about 55 miles southwest of Toledo and 47 miles northeast of Fort Wayne, Indiana, in Ohio's northwestern corner. The population was 17,066 at the 2020 census.