Tornio is a city and municipality located in the Lapland region of Finland. It covers a total area of 1,348.83 square kilometres, which includes 161.59 square kilometres of water. The municipality has a population of 20,823 people, resulting in a population density of approximately 17.52 inhabitants per square kilometre.
The city is notable for its geographical and administrative relationship with Sweden. It serves as a cross-border twin city with Haparanda, which is located on the Swedish side of the border.