The Nuclear Security Summit (NSS) is a world summit, aimed at preventing nuclear terrorism around the globe. The first summit was held in Washington, D.C., United States, on April 12–13, 2010. The second summit was held in Seoul, South Korea, in 2012. The third summit was held in The Hague, Netherlands, on March 24–25, 2014. The fourth summit was held in Washington, D.C., on March 31–April 1, 2016

Nuclear terrorism refers to any person or persons detonating a nuclear weapon as an act of terrorism. Some definitions of nuclear terrorism include the sabotage of a nuclear facility and/or the detonation of a radiological device, colloquially termed a dirty bomb, but consensus is lacking. In legal terms, nuclear terrorism is an offense committed if a person unlawfully and intentionally "uses in any way radioactive material … with the intent to cause death or serious bodily injury; or with the intent to cause substantial damage to property or to the environment; or with the intent to compel a natural or legal person, an international organization or a State to do or refrain from doing an act", according to the 2005 United Nations International Convention for the Suppression of Acts of Nuclear Terrorism.