Which document serves as the constitution of the United Nations?

The document that serves as the constitution of the United Nations is the Charter of the United Nations.
The Charter was signed on June 26, 1945, in San Francisco by 50 countries and came into effect on October 24, 1945. It established the United Nations as an international organization committed to preserving peace, promoting human rights, and fostering international cooperation.
The Charter consists of a preamble and 111 articles that outline the organization's objectives, principles, structure, and functions. It sets out the purposes and principles of the United Nations, which include maintaining international peace and security, promoting friendly relations among nations, and encouraging respect for human rights.
The Charter also establishes the main organs of the United Nations, such as the General Assembly, the Security Council, the Economic and Social Council, the Trusteeship Council, the International Court of Justice, and the Secretariat. Each organ has specific roles and responsibilities to fulfill in order to achieve the goals set out by the Charter.
In summary, the Charter of the United Nations is the document that serves as the constitution for the UN. It sets out the organization's objectives, principles, structure, and functions, and it plays a crucial role in guiding the work of the United Nations in addressing global challenges and promoting peace and cooperation among nations.