Withdrawal from the North Atlantic Treaty Organization (NATO) is the legal and political process whereby a member of the North Atlantic Treaty Organisation withdraws from the North Atlantic Treaty, and thus the country in question ceases to be a member of NATO. The formal process is stated in article 13 of the Treaty. This says that any country that wants to leave must send the United States (as the depositary state) a "notice of denunciation", which the U.S. would then pass on to the other Allies. After a one-year waiting period, the country that wants to leave would be out.

As of 2025, no member state has rescinded their membership, although it has been considered by several countries. Notwithstanding, a number of former dependencies of NATO members have never applied for membership subsequent to their becoming independent states.

Article 13 of the North Atlantic Treaty, is the article that member states use for informing other members or parties that it wishes to leave the North Atlantic Treaty Organisation. It states the following:

After the Treaty has been in force for twenty years, any Party may cease to be a Party one year after its notice of denunciation has been given to the Government of the United States of America, which will inform the Governments of the other Parties of the deposit of each notice of denunciation.

This means that after 20 years since the signing of the treaty which was in 1949, thus 1969, any member state that wishes to leave just has to inform the United States that it wants to leave, and then after a year it formally leaves.

The far-right Revival party supports Bulgarian withdrawal from NATO.

Canada is a founding member of NATO and remains a member. In 2019, the Green Party advocated a review of Canadian membership of the alliance. The position of the social-democratic New Democratic Party is complicated; while there is general support for NATO membership within the party, including from former party leaders Jack Layton and Tom Mulcair, the NDP Socialist Caucus advocates revoking Canada's membership. Some of the reasons for opposition to membership of the alliance include membership being incompatible to the Canadian tradition of peacekeeping and concerns of Canadian sovereignty over its defence forces.

As of 2022^[update], the Canadian political consensus is to support NATO membership as part of national defense policy. Parties that exist in the Canadian Parliament that support NATO membership include the governing left-of-centre Liberal Party, the opposition right-of-centre Conservative Party, and the Quebec sovereigntist Bloc Québécois.^{[citation needed]}