Tohmajärvi is a municipality of Finland. It is located in the North Karelia region. The municipality has a population of 4,066 (31 December 2023) and covers an area of 895.36 square kilometres (345.70 sq mi) of which 57.62 km2 (22.25 sq mi) is water. The population density is 4.85 inhabitants per square kilometre (12.6/sq mi). The municipality is unilingually Finnish.

North Karelia is a region in eastern Finland. It borders the regions of Kainuu, North Savo, South Savo and South Karelia, as well as Russia's Republic of Karelia. It is the easternmost region of Finland and shares a 300 kilometres (190 mi) border with Russia. The city of Joensuu is the capital and the largest settlement of the region.