Oulu (ˈoʊluː , ˈou̯lu; Uleåborg ʉːlɛɔˈbɔrj) is a city, municipality and a seaside resort of about 210,000 inhabitants in the region of North Ostrobothnia, Finland. It is the most populous city in northern Finland and the fifth most populous in the country after: Helsinki, Espoo, Tampere and Vantaa, and the fourth largest urban area in the country after Helsinki, Tampere and Turku. Oulu's neighbouring municipalities are: Hailuoto, Ii, Kempele, Liminka, Lumijoki, Muhos, Pudasjärvi, Tyrnävä and Utajärvi.
Oulu is one of the largest cities in the world for its latitude. It is the fourth northernmost city in the world with over 100,000 inhabitants, with the three others located in Russia.
Due to its large population and geopolitically economic and cultural-historical location, Oulu has been called the "capital of Northern Finland". Oulu is also considered one of Europe's "living labs", where residents experiment with new technology (such as NFC tags and ubi-screens) on a community-wide scale. Despite only ranking in the top 2% universities, the University of Oulu is regionally known in the field of information technology. Oulu has also been very successful in recent urban image surveys; in a study published by the Finnish Economic Survey in 2008, it received the best ranking of large cities in image ratings across the country, including ratings from respondents in all provinces. In the 2023 T-Media survey, Oulu was tied with Kuopio as the second most attractive city in Finland, while Tampere taking first place.
Once known for wood tar and salmon, Oulu has evolved into a major high-tech centre, particularly in IT and wellness technology. Other prominent industries include wood refining, chemicals, pharmaceuticals, paper, and steel.
Oulu has been chosen as the European Capital of Culture for 2026.
The city is named after the river Oulujoki, which originates in the lake Oulujärvi. There have been a number of other theories for the origin of the name Oulu. One possible source is a word in the Sami language meaning 'flood water', but there are other suggestions.