When did Finland and Sweden join NATO?

Russia's invasion of Ukraine prompted Finland and Sweden to apply for NATO membership in May 2022,[1] and the ratification process for Sweden is in progress.[2][3] Finland officially joined on 4 April 2023. Ukraine applied for NATO membership in September 2022 after Russia claimed to annex part of its territory.[4] Two other states have formally informed NATO of their membership aspirations: Bosnia and Herzegovina and Georgia.[5] Kosovo also aspires to join NATO.[6] Joining the alliance is a debate topic in several other European countries outside the alliance, including Austria, Ireland, Malta, Moldova, and Serbia.[7]

Finland officially joined NATO on 4 April 2023, while the ratification process for Sweden is in progress.