Claim: United Nations was named after World War 2.

The United Nations -LRB- UN -RRB- is an intergovernmental organization to promote international co-operation and to create and maintain international order . A replacement for the ineffective League of Nations , the organization was established on 24 October 1945 after World War II in order to prevent another such conflict . At its founding , the UN had 51 member states ; there are now 193 . The headquarters of the UN is in Manhattan , New York City , and experiences extraterritoriality . Further main offices are situated in Geneva , Nairobi , and Vienna . The organization is financed by assessed and voluntary contributions from its member states . Its objectives include maintaining international peace and security , promoting human rights , fostering social and economic development , protecting the environment , and providing humanitarian aid in cases of famine , natural disaster , and armed conflict . The UN is the largest , most familiar , most internationally represented and most powerful intergovernmental organisation in the world .   The UN Charter was drafted at a conference between April -- June 1945 in San Francisco , and was signed on 26 June 1945 at the conclusion of the conference ; this charter took effect 24 October 1945 , and the UN began operation . The UN 's mission to preserve world peace was complicated in its early decades by the Cold War between the US and Soviet Union and their respective allies . The organization participated in major actions in Korea and the Congo , as well as approving the creation of the state of Israel in 1947 . The organization 's membership grew significantly following widespread decolonization in the 1960s , and by the 1970s its budget for economic and social development programmes far outstripped its spending on peacekeeping . After the end of the Cold War , the UN took on major military and peacekeeping missions across the world with varying degrees of success .   The UN has six principal organs : the General Assembly -LRB- the main deliberative assembly -RRB- ; the Security Council -LRB- for deciding certain resolutions for peace and security -RRB- ; the Economic and Social Council -LRB- ECOSOC ; for promoting international economic and social co-operation and development -RRB- ; the Secretariat -LRB- for providing studies , information , and facilities needed by the UN -RRB- ; the International Court of Justice -LRB- the primary judicial organ -RRB- ; and the UN Trusteeship Council -LRB- inactive since 1994 -RRB- . UN System agencies include the World Bank Group , the World Health Organization , the World Food Programme , UNESCO , and UNICEF . The UN 's most prominent officer is the Secretary-General , an office held by Portuguese António Guterres since 2017 . Non-governmental organizations may be granted consultative status with ECOSOC and other agencies to participate in the UN 's work .   The organization won the Nobel Peace Prize in 2001 , and a number of its officers and agencies have also been awarded the prize . Other evaluations of the UN 's effectiveness have been mixed . Some commentators believe the organization to be an important force for peace and human development , while others have called the organization ineffective , corrupt , or biased .