Key UN Institutions

The UN Charter, the treaty signed in June 1945 that formed the United Nations, established six principle organs of the new international organization.

While the Trusteeship Council, created to help colonies transition to self-governance or independence, is currently inactive, the other five bodies remain key pillars of the UN system today. A description of the structure and functions of these entities is provided below.


The Security Council is the UN’s premier decision-making body, empowered to impose legally-binding obligations on Member States. Conferred by the UN Charter with “primary responsibility for the maintenance of international peace and security,” the Council has several tools at its disposal for conflict prevention and management. Chapter VI of the Charter authorizes the Council to make recommendations to resolve threats to international peace and security by various peaceful means. If unsuccessful, the Security Council may authorize enforcement measures under Chapter VII, including sanctions and military force.

The Security Council is composed of 15 Member States: five permanent members (also known as the P5), made up of the “Big Four” Allied Powers from World War II or their continuator states (the U.S., the U.K., Russia, and China) plus France; and ten rotating non-permanent members, elected to two-year terms by the UN General Assembly on the basis of equitable geographic distribution among regional groups. Votes on non-procedural matters require the concurrence of the P5, effectively giving them a veto over such decisions.

Since its establishment, the Council has served as a key forum for addressing security challenges. The Council has: authorized more than 70 peacekeeping missions in some of the world’s most dangerous places; put in place international sanctions targeting the finances and access to weapons of rogue regimes like North Korea and terrorist groups like Al-Qaeda and ISIS; and sought to deepen international cooperation on everything from terrorist financing to nuclear nonproliferation.

Nevertheless, the P5’s veto power has, at times, prevented the Council from fully asserting its role as a guarantor of global order. This was especially true when U.S.-Soviet tensions were at their height during the Cold War. While the collapse of the Soviet Union in 1991 brought on a period of increased cooperation, recent disputes over crises in Syria, Ukraine, Israel/Palestine, and Yemen have exposed ongoing divisions among the P5 and limited the Council’s effectiveness in some contexts.


Unlike the Security Council, the UN General Assembly has universal membership: all 193 UN Member States have a seat, and no country possesses veto power. While its decisions are generally non-binding, they still carry important political and moral clout, serving as a marker of the views of the international community. Over the years, the General Assembly has approved numerous noteworthy decisions, including:

  • The Universal Declaration of Human Rights (UDHR): The UDHR, a landmark document outlining basic global standards for human rights, was adopted by the General Assembly in 1948. Eleanor Roosevelt, former first lady and chair of the UN Commission on Human Rights, played a central role in drafting and shepherding the UDHR to its passage.
  • Setting the Global Development Agenda: In 2000, the General Assembly adopted the Millennium Development Goals (MDGs), a set of eight time-bound targets aimed at eradicating extreme poverty and hunger, promoting gender equality and improving access to education, and combating the spread of diseases like HIV/AIDS and malaria. In 2015, the Assembly adopted the successor to the MDGs, the Sustainable Development Goals, a new set of development objectives to build on the important progress achieved by the MDGs with a 2030 due date.

The General Assembly has a number of other important functions as well, including developing and approving the UN’s regular and peacekeeping budgets and assessment rates for Member States; electing the non-permanent members of the Security Council and other UN bodies; and appointing the Secretary-General.


The UN Secretariat is staffed by 40,000 personnel worldwide and carries out the day-to-day operations of the UN, implementing mandates adopted by the General Assembly, Security Council, Economic and Social Council, and other relevant UN bodies. Some of its main functions include:

  • Planning and managing peacekeeping and political missions;
  • Mediating international disputes;
  • Assisting implementation of Security Council sanctions;
  • Coordinating disaster relief across dozens of humanitarian agencies;
  • Promoting social and economic development and publishing related statistics and research; and
  • Facilitating discussion and meetings among the UN’s Member States.

All of this is done with an annual budget of approximately $3 billion, equal to one-third the budget of the state of Rhode Island.

The Secretariat is led by the Secretary-General, who is selected every five years by the Security Council and approved by the General Assembly. Although there is no formal limit to the number of five-year terms a Secretary-General may serve, they typically serve no more than two. The current Secretary-General is former Portuguese Prime Minister António Guterres, who assumed office on January 1, 2017.


ECOSOC is the central UN forum for discussing and formulating policy recommendations on international economic, social, cultural, educational, and health issues. According to the Charter, ECOSOC is tasked with:

  • Promoting higher standards of living, full employment, and economic and social progress;
  • Identifying solutions to international economic, social and health problems;
  • Facilitating international cultural and educational cooperation; and
  • Encouraging universal respect for human rights and fundamental freedoms.

As part of this work, ECOSOC helps to coordinate the work of the UN’s numerous specialized agencies, funds, and programs, and—by granting consultative status to non-governmental organizations—serves as a key venue through which civil society can participate in the work of the UN. ECOSOC is made up of 54 Member States who are elected to three-year terms by the General Assembly.


The ICJ is the UN’s judicial organ, composed of 15 judges elected to nine-year terms by the General Assembly and Security Council. The purpose of the ICJ is to settle, in accordance with international law, legal disputes between states. This is a key element of the international security order envisioned by the UN Charter, which commits countries to undertake several methods to peacefully resolve disputes, including judicial settlement. The ICJ also gives advisory opinions on legal questions submitted to it by other UN organs or agencies.

The ICJ does not have the authority to weigh in on any international legal dispute it wishes; instead, the Court’s ability to hear a case is derived from the consent of the Member States concerned. States involved in a dispute can accept ICJ jurisdiction in three ways:

  • Two or more states can enter into a special agreement to submit their case to the Court; or
  • A jurisdictional clause in a treaty may require countries that have ratified the treaty to submit disagreements over interpretation or application of the document to the Court (more than 300 treaties, both bilateral and multilateral, contain such clauses); or
  • A state may submit a unilateral declaration accepting the Court’s jurisdiction as compulsory in the event of a dispute with another state that has made a similar commitment.

Member States are bound to comply with ICJ decisions in any case to which they are a party. According to the Charter, if a Member State fails to perform its obligations under an ICJ judgment, the case can be referred to the Security Council, which can then apply enforcement measures. Over the years, the U.S. has been involved in several cases before the Court. In 1980, for example, the ICJ ordered Iran to pay reparations to the U.S. over the 1979 hostage crisis.