Member states of the United Nations

The United Nations comprise sovereign states and the world's largest intergovernmental organization. All members have equal representation in the United Nations General Assembly.
The Charter of the United Nations defines the rules for admission of member states. Membership is open to all states which accept certain terms of the charter and are able to carry them out. New members must be recommended by the United Nations Security Council. In addition to the member states, the UN also invites non-member states to be observer states at the UN General Assembly. A member state that has persistently violated the principles of the United Nations Charter can be expelled from the United Nations.

Membership

The criteria for admission of new members to the UN are established in Chapter II, Article 4 of the UN Charter:

Membership in the United Nations is open to all states which accept the obligations contained in the present Charter and, in the judgement of the Organization, are able and willing to carry out these obligations.
The admission of any such state to membership in the United Nations will be effected by a decision of the General Assembly upon the recommendation of the Security Council.

A recommendation for admission from the Security Council requires affirmative votes from at least nine of the council's fifteen members, with none of the five permanent members using their veto power. The Security Council's recommendation must then be approved in the General Assembly by a two-thirds majority vote.
In principle, only sovereign states can become UN members, and currently, all UN members are sovereign states. Although five members were not sovereign when they joined the UN, they all subsequently became fully independent between 1946 and 1991. Because a state can only be admitted to membership in the UN by the approval of the Security Council and the General Assembly, a number of states that are considered sovereign according to the Montevideo Convention are not members of the UN. This is because the UN does not consider them to possess sovereignty, mainly due to the lack of international recognition or due to opposition from one of the permanent members.
In addition to the member states, the UN also invites non-member states to become observer states at the UN General Assembly, allowing them to participate and speak in General Assembly meetings, but not vote. Observers are generally intergovernmental organizations and international organizations and entities whose statehood or sovereignty is not precisely defined.

Original members

The UN officially came into existence on 24 October 1945, after ratification of the United Nations Charter by the five permanent members of the United Nations Security Council and a majority of the other signatories. A total of 51 original members joined that year; 50 of them signed the Charter at the United Nations Conference on International Organization in San Francisco on 26 June 1945, while Poland, which was not represented at the conference, signed it on 15 October 1945.
The original members of the United Nations were: France, Russia, China, the United Kingdom, the United States—these first five forming the Security Council—Argentina, Australia, Belarus, Belgium, Bolivia, Brazil, Canada, Chile, Colombia, Costa Rica, Cuba, Czechoslovakia, Denmark, the Dominican Republic, Ecuador, Egypt, El Salvador, Ethiopia, Greece, Guatemala, Haiti, Honduras, India, Iran, Iraq, Lebanon, Liberia, Luxembourg, Mexico, the Netherlands, New Zealand, Nicaragua, Norway, Panama, Paraguay, Peru, the Philippines, Poland, Saudi Arabia, South Africa, Syria, Turkey, Ukraine, Uruguay, Venezuela and Yugoslavia.
Among the original members, 49 are either still UN members or had their memberships in the UN continued by a successor state '; for example, the membership of the Soviet Union was continued by the Russian Federation after its dissolution '. The other two original members, Czechoslovakia and Yugoslavia, had been dissolved and their memberships in the UN not continued from 1992 by any one successor state '.
At the time of UN's founding, the seat of China in the UN was held by the Republic of China, but as a result of United Nations General Assembly Resolution 2758 in 1971, it is now held by the People's Republic of China '.
A number of the original members were not sovereign when they joined the UN, and only gained full independence later:

Belarus and Ukraine were both constituent republics of the Soviet Union, until gaining full independence in 1991.
India was under British colonial rule, until gaining full independence in 1947.
New Zealand, while de facto sovereign at that time, "only gained full capacity to enter into relations with other states in 1947 when it passed the Statute of Westminster Adoption Act. This occurred 16 years after the British Parliament passed the Statute of Westminster Act in 1931 that recognised New Zealand's autonomy. If judged by the Montevideo Convention criteria, New Zealand did not achieve full de jure statehood until 1947." However, the UN considers New Zealand to have been independent in 1945, at the time the UN was formed.
The Philippines was a commonwealth with the United States, until gaining full independence in 1946.
Current members

Member state

Date of admission

Notes

Package deal

The start of the Cold War led to membership conflicts almost immediately, with the United States refusing to admit countries in Eastern Europe while the Soviet Union refused to admit countries in Western Europe. Starting as early as January 1946, the United States used its "automatic majority" on the Security Council to refuse the application of Albania without a veto, while the Soviet Union vetoed the applications of Ireland, Portugal and Finland. The Soviet Union also vetoed the applications of Jordan and Ceylon, stating that it did not believe they were sufficiently independent from the United Kingdom.
Starting in September 1949, the Soviet Union began to veto the applications of some neutral countries such as Nepal as well, stating that it would not admit them until its preferred applicants were also admitted. Both the United States and Soviet Union stated that they were willing to admit each other's preferred applicants, but the United States demanded that Western European applicants be voted on first while the Soviet Union demanded that Eastern European applicants be voted on first. Both superpowers refused to allow multiple applicants to be voted on simultaneously.
The impasse continued until the death of Stalin caused a brief thaw in the Cold War. By this time, 18 applications had been blocked, and the superpowers stated that they would no longer oppose a simultaneous vote. The veto of Mongolia by the Republic of China delayed the proceedings by one day, with the Soviet Union offering to exclude Mongolia from the list of 18 if Japan were also excluded. The United States abstained on the offering. In what was widely described as a "package deal", the remaining 16 countries were simultaneously admitted to the United Nations on 14 December 1955.

Former members

Republic of China (1945–1971)

The Republic of China joined the UN as an original member on 24 October 1945, and as set out by the United Nations Charter, Chapter V, Article 23, became one of the five permanent members of the United Nations Security Council. In 1949, as a result of the Chinese Civil War, the Kuomintang-led ROC government lost effective control of mainland China and relocated to the island of Taiwan, and the Communist Party-led government of the People's Republic of China, declared on 1 October 1949, took control of mainland China. The UN was notified on 18 November 1949 of the formation of the Central People's Government of the People's Republic of China; however, the Government of the Republic of China continued to represent China at the UN, despite the small size of the ROC's jurisdiction of Taiwan and a number of smaller islands compared to the PRC's jurisdiction of mainland China. As both governments claimed to be the sole legitimate representative of China, proposals to effect a change in the representation of China in the UN were discussed but rejected for the next two decades. Both sides rejected compromise proposals to allow both states to participate in the UN, based on the One-China policy.
By the 1970s, a shift had occurred in international diplomatic circles and the PRC had gained the upper hand in international diplomatic relations and recognition count. On 25 October 1971, the 21st time the United Nations General Assembly debated on the PRC's admission into the UN, United Nations General Assembly Resolution 2758 was adopted, by which it recognized that "the representatives of the Government of the People's Republic of China are the only lawful representatives of China to the United Nations and that the People's Republic of China is one of the five permanent members of the Security Council," and decided "to restore all its rights to the People's Republic of China and to recognize the representatives of its Government as the only legitimate representatives of China to the United Nations, and to expel forthwith the representatives of Chiang Kai-shek from the place which they unlawfully occupy at the United Nations and in all the organizations related to it." This effectively transferred the seat of China in the UN, including its permanent seat on the Security Council, from the ROC to the PRC, and expelled the ROC from the UN.
In addition to losing its seat in the UN, the UN Secretary-General concluded from the resolution that the General Assembly considered Taiwan to be a province of "China", which refers to the Greater China region. Consequently, the Secretary-General decided that it was not permitted for the ROC to become a party to treaties deposited with it.