Oulu is a major port city in Finland and the regional capital of North Ostrobothnia. It is located on the north-western coast of the country, at the mouth of the River Oulu. The population of Oulu is approximately 217,000, while the sub-region has a population of approximately 265,000. It is the 5th most populous municipality in Finland, and the fourth most populous urban area in the country. Oulu is also the most populous city in Northern Finland.