Porkkalanniemi (Swedish: Porkala udd) is a peninsula in the Gulf of Finland located at Kirkkonummi (Kyrkslätt) in Southern Finland.
The peninsula had great strategic value, as coastal artillery based there would be able to reach more than halfway across the Gulf of Finland. If the same power controlled the Estonian coast, on the opposite side of the gulf, it would then be able to block Saint Petersburg's naval access to the Baltic Sea. The distance to Estonia at the closest point is only 36 km (22 mi). Porkkala is furthermore located only 30 kilometers (19 mi) from Helsinki, the Finnish capital, and a foreign power based there would be able to exert significant pressure on the Finnish government.
Nowadays the coasts of the peninsula are popular bird watching areas during spring migration as the Arctic geese and other waterfowl are on their passage.
At the end of the Second World War the Soviet Union secured the rights of lease to a naval base at Porkkala, in accordance with the Moscow armistice agreement that ended the Continuation War, between Finland and the Soviets on September 19, 1944. Porkkala thus replaced the peninsula of Hanko, which had been leased to the Soviets as a naval base in 1940–41. A large area centered on the peninsula, including land from the municipalities of Kirkkonummi, Siuntio and Ingå and almost the entire area of Degerby, was leased to the USSR from 29 September 1944, ten days after the armistice. It was immediately placed under a military commander, Neon Vasilyevich Antonov (1907–1948), who remained in office till June 1945, when he was transferred to command the Amur River flotilla, in preparation for the war against Japan.
According to the armistice of 1944, the area was leased to the Soviet Union for 50 years. On February 10, 1947, the Paris peace treaty reaffirmed the Soviet Union's right to occupy this area until 1994.
No Soviet civilian administration was set up, the USSR simply administered it through the military commander of Porkkala, a post held until 26 January 1956 by Sergey Ivanovich Kabanov (1901–1973), the former Commander of Hanko naval base.
While under Soviet control, Finnish passenger trains running between Helsinki and Turku were allowed to use the line through the area. However all train windows had to be closed with shutters, and photography was prohibited.
During the 1952 Summer Olympics in Helsinki, the Soviet Olympic team was housed on the base rather than in the Olympic village.
Although the Soviet lease for Porkkala had been conceded for 50 years, an agreement was reached to return it earlier. The agreement was signed on September 19, 1955, exactly 11 years after the armistice, and control of the area was handed back to Finland on January 26, 1956. This may be attributed to the process of Finlandization and to technological progress making coastal artillery obsolete, but the renunciation of Stalinism by the Soviet Union under Nikita Khrushchev and the fact that Finland had undertaken to adopt neutrality and so remain out of NATO were also important contributing factors.
At present, the Porkkala area houses one of the main bases of the Finnish Navy, located in Upinniemi, near Porkkala proper.