"Five are considered to be "nuclear weapons states", an internationally recognized status conferred by the Nuclear Non-Proliferation Treaty (NPT). In order of acquisition of nuclear weapons these are: the United States, Russia (successor state to the Soviet Union), the United Kingdom, France, and China.

Since the NPT entered into force in 1970, three states that were not parties to the Treaty have conducted nuclear tests, namely India, Pakistan, and North Korea. North Korea had been a party to the NPT but withdrew in 2003. Israel is also widely believed to have nuclear weapons, though it has refused to confirm or deny this.[1] The status of these nations is not formally recognized by international bodies as none of them are currently parties to the NPT. South Africa has the unique status of a nation which developed nuclear weapons but has since disassembled its arsenal before joining the NPT."