The Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty (NPT) is the cornerstone of the nuclear nonproliferation regime. The NPT entered into force on March 5, 1970, was extended indefinitely in 1995, and has become nearly universal. This Treaty has made the world safer and more prosperous, and it remains one of the most successful treaties ever negotiated. | U.S. Department of State