Suomussalmi is a municipality located in the Kainuu region of Finland. It is situated approximately 90 kilometres northeast of Kajaani, which serves as the capital of the Kainuu region, and 120 kilometres south of Kuusamo.
The municipality covers a total area of 5,857.60 square kilometres, of which 587.03 square kilometres is water. As of December 31, 2025, the population stands at 6,957 residents, resulting in a population density of 1.32 inhabitants per square kilometre. The region is unilingually Finnish, and Ämmänsaari serves as the largest built-up area within the municipality.