The Finnish nickel deposits were found in the Petsamo area near the Barents Sea. Until the Paris Peace Treaties, 1947, this was the northernmost part of Finland. In 1934 it was estimated that the deposits contained over five million tons of nickel. In 1935, Canadian and French corporations began mining operations there.
The nickel deposits were a lesser known reason for Allied and German interest in the area during World War II, as potentially of great importance for production of arms and munitions. Both the planned Franco-British support of Finland in the Winter War, and German occupation of Denmark and Norway (Operation Weserübung) were partly motivated by control of the nickel mines.
During the period between the Winter War and the German invasion of the Soviet Union in 1941, there were disputes between Finland and the Soviet Union over mining rights in Petsamo. Finland refused to allow the Soviet Union to mine nickel in Petsamo. This was one of the causes of hostility between the Soviet Union and Finland, which led to the Continuation War. As part of the German invasion, troops from Norway occupied the Petsamo region in 1941, securing the nickel supply.
The Continuation War ended in September 1944, with the Moscow armistice of 19th September 1944. Finland ceded Petsamo to the Soviet Union. All subsequent nickel production there has been under Soviet or Russian authority.
For the geology of Finnish nickel deposits see,
In more recent years, several small nickel deposits have been mined in other parts of Finland.
All of these deposits were mined by Outokumpu.