Columbiana County is a county located in the U.S. state of Ohio. As of the 2020 census, the population was 101,877. The county seat is Lisbon and its largest city is Salem. Created in 1803, the county name is derived from that of 15th-century Italian explorer Christopher Columbus. Columbiana County comprises the Salem, OH Micropolitan Statistical Area, which is also included in the larger Youngstown–Warren–Salem, OH Combined Statistical Area.