Member states of the League of Nations

Between 1920 and 1946, a total of 63 countries became member states of the League of Nations.

When the Assembly of the League of Nations first met, it consisted of 42 founding members. A further 21 countries joined between then and the dissolution of the League.

As several countries withdrew from the League over its existence, the 63 countries were never all members at the same time. The League's greatest extent was from 28 September 1934 (when Ecuador joined) to February 1935 (when Paraguay withdrew) with 58 countries. At this time, only Costa Rica (December 1924), Brazil (June 1926), Japan (March 1933), and Germany (October 1933) had withdrawn, and only Egypt joined later (on 26 May 1937).

Founding members
The Covenant of the League of Nations was part of the Treaty of Versailles, signed on 28 June 1919 between the Allies of World War I and Germany. In order for the treaty to enter into force, it had to be deposited at Paris; in order to be deposited, it had to be ratified by Germany and any three of the five Principal Powers (the United States of America, the British Empire, France, Italy, and the Empire of Japan). Any Allied signatory that ratified the treaty would automatically join the League.

Germany was forced to ratify the treaty first, which it did on 10 July 1919. Italy ratified on 7 October 1919, the British Empire and its colonies ratified on 10 October 1919, and France ratified on 12 October 1919. These ratifications were deposited (along with ten other countries' ratifications) on 10 January 1920. All but three of the remaining signatories (the United States, Ecuador, and the Kingdom of Hejaz) ratified by the time the Assembly first met on 15 November 1920.

The Covenant also invited 13 neutral nations to join the League. To join, an invitee had to agree ("accede without reservation") to the Covenant within two months of the League's founding. All 13 invitees accepted their invitations within the two-month deadline; four of them accepted their invitations even before the League was founded.

The United States Senate voted 4935 in favor of ratification, but this failed to reach the necessary two-thirds majority. Hejaz (later Saudi Arabia) also never ratified the treaty. Ecuador would not ratify the treaty until 1934. As an original Allied signatory, Ecuador was entitled to join the League this way with no deadline or Assembly vote, and the League considered Ecuador to still be a founding member.

Uniquely, China (then the Beiyang government) joined the League by ratifying the Treaty of St. Germain (with Austria) instead of the Treaty of Versailles (with Germany), as both treaties included the Covenant of the League of Nations. It had refused to sign the Treaty of Versailles due to it giving the previously-German-controlled Shandong colony in China to the Empire of Japan.

Additional members could join the League by a two-thirds vote of the Assembly.

List
The members below are listed in the order matching the Covenant (signatories first, followed by invitees), except for Ecuador. The colonies of the British Empire immediately followed it and did not sign in alphabetical order. Czecho-Slovakia and El Salvador were alphabetized under 'S'.

A country was allowed to send a withdrawal notice at any time, but it would take two years to go into effect after the League received it, and the country would keep both its obligations and membership during the interim. In practice, a withdrawing country quit the League immediately, and was absent from all sessions and votes for the last two years of its formal membership. The "Date of withdrawal" column shows when the withdrawal notice was sent.

Expulsion of the Soviet Union
On 14 December 1939, the Soviet Union was expelled for invading Finland in violation of the Covenant of the League of Nations, by a Council vote of 7-0-4-3 (7 in favor, 0 against, 4 abstaining, 3 absent). The United Kingdom, France, Belgium, Bolivia, the Dominican Republic, South Africa, and Egypt voted in favor; the Republic of China, Finland, Greece, and Yugoslavia abstained; and Iran, Peru, and the Soviet Union itself were absent. Three of the votes in favor had been made Council members the day before the vote (South Africa, Bolivia, and Egypt). This was one of the League's final acts before it practically ceased functioning.

It has been disputed whether the expulsion was legally valid. Article 16 paragraph 4 of the Covenant states that the Council may expel a member from the League if all members of the Council other than the to-be-expelled member concur. However, it is unclear if abstentions or absences are permitted for expulsion votes (though it is undisputed that they are allowed for non-expulsion unanimous Council decisions). Even if permitted, it is disputed whether the expulsion could be legally valid without a majority (8 out of 14) of the Council in favor.

Regardless, both the expulsion and dispute had little practical effect. The Soviet Union had already declared nine days earlier that it would be absent from the League until further notice, it acknowledged its expulsion and made no move to challenge it on the disputed grounds, no other member was ever expelled from the League to demonstrate any precedent, and the League took no further significant actions due to the Second World War.

Non-members
Between November and December 1920, Armenia, Azerbaijan, Georgia, and Ukraine applied for membership amid the dissolution of the Russian Empire and the Russian Civil War, but were denied because they did "not appear to have a stable government whose authority extends over the whole of its territory". (Some extra consideration was given to Armenia due to it being a signatory of the Treaty of Sèvres, which would have given Armenia some territory from the broken-up Ottoman Empire, but the treaty failed to be ratified.) Estonia, Latvia, and Lithuania also applied in 1920 and were denied that year because they "had not achieved a definite international status" at the time (the three would be admitted the next year).

Some of the European microstates, namely Liechtenstein, Monaco, and San Marino, also applied for membership but were denied, explicitly due to their "small size". Andorra and Vatican City never sought membership.

Iceland was given the opportunity to join the League of Nations in 1920, but opted not to, primarily due to limited administrative resources.

Some relatively-isolated sovereign states in Asia also did not join, including Bhutan, Nepal, and Yemen, at least in part due to having no diplomatic relations with the major powers. Tibet and Mongolia were de facto independent, but their independence was not recognized by the major powers.

At the IX Congress of European Nationalities, an organization of the League of Nations, held in Bern, the first three autonomies of Spain (Basque Country, Galicia, and Catalonia), were recognized as a nation. In any case, they were not independent but were represented by the Spanish government.

World War II and aftermath
Several member states were occupied or annexed during World War II, during which the League was largely paralyzed and held no sessions or votes. With the exception of the Anschluss, the League did not recognize any of these occupations, and the occupied states remained members of the League on paper. With the exception of Vichy France (later rescinded by Free France), the League also did not recognize any notices of withdrawal sent by puppet regimes, considering them to have been sent under duress. Not all puppet regimes attempted to withdraw.

The membership table above notes occupations that began before the start of World War II in Europe, those that continued after the end of World War II, and those whose puppet states attempted to withdraw. For brevity, the several occupations that do not meet any of these criteria (such as in the case of Luxembourg) are not listed.

The 20th annual session of the Assembly took place in 1939, but the 21st session did not take place until April 1946, after which the League ceased to exist. During this last session, 35 out of 44 League members attended, with Albania, Bulgaria, Ethiopia, Iraq, Liberia, Thailand, and the Baltic states not present. (Colombia was present, but only as a non-voting observer as its government had not authorized its representative on whether to vote for or against the dissolution of the League. Allied-occupied Austria was also permitted to send an observer with approval from its occupiers and the rest of the League.)

The League partially did not recognize the Soviet occupation of the Baltic states, which were the only member states of the League to remain occupied after the end of World War II. In its last session, Estonia, Latvia, and Lithuania remained on the list of members of the League. However, two months before the session, the League stated that it would not consider the 1939 documents of any representatives as valid, and required the governments of the League members to furnish new documents naming representatives. When the representatives of the Latvian government-in-exile and Lithuanian government-in-exile attempted to attend the session, a Secretariat staff member denied their 1939 documents as instructed, and explicitly stated that there did not exist any government which could provide them with the necessary credentials. The letter documenting this incident refers to the representatives as the "permanent delegate of Latvia" and "permanent delegate of Lithuania" as titles. (The letter does not mention the presence of the delegate of Estonia.) The staff member offered the representatives, and their family members and assistants, entry into the League's diplomatic gallery to spectate the session, but the representatives refused the offer for themselves, while accepting it for their family members and assistants. In addition, the offered entry card, and even the envelope containing the card, explicitly omitted a country name and a title.

The League of Nations was formally dissolved on 18 April 1946; its assets and responsibilities were transferred to the United Nations.

Map
[[File:LN member states animation.gif|thumb|800px|center|A map of the world in the years 1920–1945, which shows the League of Nations members during its history.

{{legend|#002255|Members}}{{legend|#0066FF|Colonies of members}}

{{legend|#ff6600|Mandates}}

{{legend|#b3b3b3|Non-members}} {{legend|#cccccc|Colonies of non-members}} ]]