The city of Oulu, Finland, is founded by Charles IX of Sweden.

Oulu is a city in Finland and the regional capital of North Ostrobothnia. It is located on the northwestern coast of the country at the mouth of the River Oulu. The population of Oulu is approximately 216,000, while the sub-region has a population of approximately 264,000. 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.

Charles IX, also Carl, reigned as King of Sweden from 1604 until his death. He was the youngest son of King Gustav I and of his second wife, Margaret Leijonhufvud, the brother of King Eric XIV and of King John III, and the uncle of Sigismund, who became king both of Sweden and of Poland. By his father's will Charles received, by way of appanage, the Duchy of Södermanland, which included the provinces of Närke and Värmland; but he did not come into actual possession of them till after the fall of Eric and the succession to the throne of John in 1569.

April 8 is the 98th day of the year in the Gregorian calendar; 267 days remain until the end of the year.