Treaty on the Prohibition of the Emplacement of Nuclear Weapons and Other Weapons of Mass Destruction on the Sea-Bed and the Ocean Floor and in the Subsoil thereof

The Seabed Arms Control Treaty (or Seabed Treaty, formally the Treaty on the Prohibition of the Emplacement of Nuclear Weapons and Other Weapons of Mass Destruction on the Sea-Bed and the Ocean Floor and in the Subsoil thereof) is a multilateral agreement between the United States, Soviet Union (now Russia), United Kingdom, and 91 other countries banning the emplacement of nuclear weapons or "weapons of mass destruction" on the seabed and the ocean floor beyond a 12 nautical miles (22.2 km; 13.8 mi) coastal zone. It allows signatories to observe all seabed "activities" of any other signatory beyond the 12-mile zone to ensure compliance.

Like the Antarctic Treaty, the Outer Space Treaty, and the Nuclear-Weapon-Free Zone treaties, the Seabed Arms Control Treaty sought to prevent the introduction of international conflict and nuclear weapons into an area hitherto free of them. Reaching agreement on the seabed, however, involved problems that were not met in framing the other two agreements, for example while the Soviet Union initially desired the banning of all military activity including sensors detecting submarine movements, the United States desired the more limited "workable, verifiable and effective agreement to bar the use of the seabed for the emplacement of weapons of mass destruction."