Nuclear peace is a theory of international relations which argues that the presence of nuclear weapons may in some circumstances decrease the risk of crisis escalation, since parties will seek to avoid situations that could lead to the use of nuclear weapons. Proponents of nuclear peace theory therefore believe that controlled nuclear proliferation may be beneficial for global stability. Critics argue that nuclear proliferation increases the chance of nuclear war through either deliberate or in-deliberate use of nuclear weapons, as well as the likelihood of nuclear material falling into the hands of violent non-state actors.

The major debate on the issue has been between Kenneth Waltz, the founder of neorealist theory in international relations, and Scott Sagan, a leading proponent of organizational theories in international politics. Waltz generally argues that "more may be better" and contends that new nuclear states will use their acquired nuclear capabilities as nuclear deterrence and thus preserve peace. Sagan argues that "more will be worse" since new nuclear states often lack adequate organizational controls over their new weapons, which makes for a high risk of deliberate or accidental nuclear war or of theft of nuclear material by terrorists to perpetrate nuclear terrorism.