What is the name of the treaty that is designed to limit the spread of nuclear weapons and that has been signed by 190 countries?

The Nuclear Non-Proliferation Treaty (NPT) is the international agreement intended to prevent the spread of nuclear weapons. It has been joined by 190 countries, matching the description in the question. SALT I and SALT II were arms-control agreements between the United States and the Soviet Union, while the International Atomic Energy Act is not the treaty described.

AI-written and checked against the verified answer.