What was the name of the 1963 US-Soviet treaty banning atmospheric nuclear tests?

The 1963 US-Soviet treaty banning atmospheric nuclear tests was the Limited Test Ban Treaty. Its formal title was the Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water, and it is also commonly called the Partial Test Ban Treaty.

Signed in Moscow on August 5, 1963, the agreement prohibited nuclear detonations in the atmosphere, outer space, and underwater. Underground tests were still allowed because negotiators could not agree on reliable verification and inspection arrangements for detecting them.

The treaty followed years of public concern about radioactive fallout, intensified by the 1954 Castle Bravo test and the 1961 Soviet Tsar Bomba test. The United States, Soviet Union, and United Kingdom were the original signatories; the treaty entered into force on October 10, 1963.

A common mix-up is the Comprehensive Nuclear-Test-Ban Treaty, or CTBT. The CTBT seeks to ban all nuclear explosions, including underground tests, while the 1963 treaty was only a partial or limited ban.