Tornio is a city and municipality in Lapland, Finland. The city forms a cross-border twin city together with Haparanda on the Swedish side. The municipality covers an area of 1,348.83 square kilometres, of which 161.59 km² is water. The population density is 18.08 inhabitants per square kilometre, with a total population of 21,466. It borders the Swedish municipality of Haparanda.
In spite of being a border city Tornio is unilingually Finnish with a negligible number of native Swedish speakers, although this does not count vast numbers of bilinguals who speak Swedish as a second language, with an official target of universal working bilingualism for both border municipalities.