Finland–NATO relations

Finland has been a member of the North Atlantic Treaty Organization (NATO) since 4 April 2023.

In the aftermath of World War II, following the formation of NATO in 1949 and throughout the Cold War, Finland maintained a position of neutrality, in what became known as Finlandization, in the face of its often complicated relations with the Soviet Union.

The possibility of membership became a topic of debate in the country after the end of the Cold War and following the country's accession to NATO's Partnership for Peace (PfP) programme and the European Union (EU) in the mid-1990s. In spite of these new bonds to Europe and the West, public support for NATO accession remained low.

The 2022 Russian invasion of Ukraine marked a turning point in the debate, and swung public opinion in favour of NATO membership. Along with neighboring Sweden, the country applied to join NATO on 18 May 2022. Following ratification, Finland became a member of NATO on 4 April 2023. Finland has a 1,340-kilometre (830 mi) border with Russia, which upon accession more than doubled NATO's pre-existing border with Russia.