Suomenniemi is a former municipality of Finland. It was consolidated with Mikkeli on 1 January 2013.

It was located in the province of Southern Finland and was part of the South Karelia region. The municipality had a population of 763 (31 December 2012) and covered an area of 362.96 square kilometres (140.14 sq mi) of which 79.24 km (30.59 sq mi) is water. The population density is 2.6893/km (6.965/sq mi). The municipality had the smallest population of the Finnish mainland.