Posio is a municipality of Finland. It is located in the region of Lapland. The municipality has a population of 2,826 (31 December 2025) and covers an area of 3,544.90 square kilometres (1,368.69 sq mi) of which 506.14 km2 (195.42 sq mi) is water. The population density is 0.93 inhabitants per square kilometre (2.4/sq mi). Neighbour municipalities are Rovaniemi, Kemijärvi, Ranua, Salla, Kuusamo, Taivalkoski and Pudasjärvi.