Nuclear weapons of the United States

The United States holds the second largest arsenal of nuclear weapons among the nine nuclear-armed countries. Under the Manhattan Project, the United States became the first country to manufacture nuclear weapons and remains the only country to have used them in combat, with the bombings of Hiroshima and Nagasaki in World War II against Japan. In total it conducted 1,054 nuclear tests, the most of any country. It is an original party to and one of the five "nuclear-weapon states" recognized by the 1968 Treaty on the Non-Proliferation of Nuclear Weapons.

As of 2025, the US and Russia possess a comparable number of warheads; together more than 90% of the world's stockpile. The US holds in total 5,177 warheads, of which 3,700 are stockpiled, and 1,477 are awaiting dismantlement. Of the stockpile, 1,770 are deployed, while 1,930 are held in reserve. The President of the United States has the sole authority to use nuclear weapons, and US policy permits nuclear first use.

The US stockpile is mostly under Strategic Command, assigned to its nuclear triad: 1,920 to 280 Trident II submarine-launched ballistic missiles aboard 14 Ohio-class submarines, 800 to 400 silo-based Minuteman III intercontinental ballistic missiles, and 780 B61 and B83 bombs and AGM-86B cruise missiles to 19 B-2 Spirit and 46 B-52 Stratofortress bombers respectively. The US plans to modernize its triad with the Columbia-class submarine, Sentinel ICBM, and B-21 Raider, from 2029. Early warning is provided by various radars including Solid State Phased Arrays and satellites including the Space-Based Infrared System. The Missile Defense Agency maintains a limited anti-ballistic missile capability via the Ground-Based Interceptor and Aegis systems.

Additionally, 200 B61 bombs are available for tactical nuclear use by fighter aircraft. The US currently stations approximately 100 of these nuclear weapons in six European NATO countries: Belgium, Germany, Italy, the Netherlands, Turkey, and United Kingdom. The US extends a nuclear umbrella to South Korea, Japan, and Australia.

Throughout the Cold War, the US and USSR competed in the nuclear arms race. From 1951, the US became the first country to develop thermonuclear weapons. From the 1950s, the US positioned nuclear weapons in at least 17 other nations, including NATO allies, South Korea, Japan, Taiwan, and the Philippines, while Strategic Air Command operated hundreds of strategic bombers, under the policies of massive retaliation and containment of Eastern Bloc countries. By the 1960s, ICBMs were deployed in silos, such as the Atlas and Titan, and aboard submarines as Polaris. The 1962 Cuban Missile Crisis is regarded as one close call that threatened nuclear weapons use and cemented the concept of mutually assured destruction. The arsenal grew in the 1980s, alongside the proposed Peacekeeper ICBM and space-based Strategic Defense Initiative missile defense system. When the Cold War ended, all Army and surface Navy nuclear weapons were withdrawn. The arsenal was also limited by bilateral treaties, beginning with START I. Its successor, New START, expired in 2026. Since 2025, the US has pursued the space-based Golden Dome missile defense system.

Between 1940 and 1996, the US spent over US$11.9 trillion in present-day terms on nuclear weapons infrastructure, and nuclear forces maintenance is projected to cost $60 billion per year from 2021 through 2030. The US produced over 70,000 nuclear warheads, more than all other states combined. Design takes place at Los Alamos, Livermore, and Sandia laboratories; tests were conducted at Nevada Test Site and Pacific Proving Grounds. Until the 1963 Partial Nuclear Test Ban Treaty, the vast majority of tests were atmospheric. Subsequent underground testing limited nuclear fallout. Nuclear sites radioactively contaminated civilian communities: the US government compensated Marshall Islanders over US$759 million for testing exposure, and US citizens over US$2.5 billion. The US began a testing moratorium in 1992 and signed the Comprehensive Nuclear-Test-Ban Treaty in 1996, but has not ratified it. Stockpile Stewardship is the current warhead maintenance program, using experiments including supercomputer simulation and inertial confinement fusion.