Alliance is a city in Stark County, Ohio, United States. The population was 21,672 at the 2020 census. It was established in 1854 by the merger of three smaller communities and was a manufacturing and railroad hub in the 20th century. Alliance is associated with the state flower of Ohio, the scarlet carnation, and is known as the "Carnation City". The University of Mount Union, a private liberal arts college established in 1846, is located in the city. Partially extending into Mahoning County, Alliance is part of the Canton–Massillon metropolitan area.