The United Nations (UN) is an international organization founded in 1945 to promote peace, security, human rights, and development. It replaced the League of Nations and has 193 member states. The UN's main bodies are the General Assembly, Security Council, Economic and Social Council, Secretariat, and International Court of Justice. Over the years, the UN has worked to prevent conflicts, provide humanitarian aid, and promote sustainable development around the world. It has also played a key role in addressing global challenges such as climate change, poverty, and health emergencies. The UN has received both criticism and praise for its efforts, but remains a fundamental force for international cooperation and diplomacy.