Oulujoki is a river in Oulu province, Finland. Its name in Finnish means literally "Oulu River" (Swedish: Ule älv), originally in old Northern Ostrobothnian dialect literally "Flood River". Its origin is Oulujärvi and its watershed area covers a significant part of Kainuu region. It flows into the Bothnian Bay at Oulu. Port of Oulu is located at the mouth of the river.