Hanko (hängˈkō) [key] or Hangö hängˈö, city (1996 pop. 10,623), Southern Finland prov., SW Finland, at the tip of the Hanko peninsula on the Baltic Sea. A popular bathing resort and a manufacturing town, it is the most important winter port in Finland. It was leased to the Soviet Union for 30 years as a naval base after the Finnish-Russian War (1939–40). The USSR exchanged it for a 50-year lease on the Porkkala district in 1944; however, in 1956 the Soviet Union evacuated Porkkala.