Seinäjoki is a city in Finland and the regional capital of South Ostrobothnia. Seinäjoki is located in the western interior of the country and along the River Seinäjoki. The population of Seinäjoki is approximately 66,000, while the sub-region has a population of approximately 132,000. It is the 16th most populous municipality in Finland, and the 13th most populous urban area in the country.

South Ostrobothnia is one of the 19 regions of Finland. It borders the regions of Ostrobothnia, Central Ostrobothnia, Central Finland, Pirkanmaa, and Satakunta. Among the Finnish regions, South Ostrobothnia is the ninth largest in terms of population. Seinäjoki is the regional centre and by far the largest city in the area.