From the very beginning, the development and construction of nuclear weapons have been accompanied by the need to conduct nuclear tests to ensure that the nuclear reaction and the system work as intended. It is considered almost impossible to achieve a functioning nuclear weapons capability without nuclear tests. The world’s first nuclear test was carried out at a test site in New Mexico in the United States in July 1945. Since then, a total of 2,121 nuclear tests have been carried out. Of these tests, the United States conducted 1,032 tests, the Soviet Union 727, France 215, Britain 88, China 47, North Korea 6, India 3, and Pakistan 2. About a quarter of all nuclear tests have been carried out in the atmosphere, while the rest took place underground or underwater.

The United States and the Soviet Union conducted their nuclear tests in their own areas, albeit in areas as remote as possible. The two most important nuclear test sites used by the United States have been the Nevada Desert, where more than 900 nuclear tests have been conducted, and the US-owned Marshall Islands in the Pacific Ocean, where more than 40 nuclear tests have been conducted. The most famous of these was the 10–15 megaton hydrogen bomb test carried out on Bikini Atoll in 1954, which was the largest nuclear explosion carried out by the United States. In addition, the United States has conducted more than 20 nuclear tests in the Pacific Ocean, the Christmas Islands, and the Johnston Islands, as well as individual nuclear tests in Colorado, Mississippi, Alaska, and the South Atlantic.

The Soviet Union has only used two nuclear testing sites. The highest number of nuclear explosions was carried out at the Semipalatinsk test site in the former Kazakh Soviet Republic, in Central Asia, where more than 450 nuclear tests were carried out between 1949 and 1989. Another widely used test site has been the island of Novaya Zemlya in the Soviet Arctic, only 900 kilometres from Finland. More than 130 nuclear tests have been carried out there, the most famous of which was the huge 50-megaton hydrogen bomb explosion in 1961.

For understandable reasons, neither Britain nor France conducted nuclear tests within their European territories. Between 1952 and 1969, Britain conducted a total of 45 nuclear tests, the first 12 being in Australia in three different regions, nine in the Pacific, and 24 in Nevada, the United States, as part of a joint program between the British and the Americans. The first two British nuclear tests in Australia were conducted without prior consultation with the Australian government. From the third test onward, a formal agreement was reached with Australian authorities. Nevertheless, Australia became increasingly reluctant to host British nuclear testing activities. As a result, the United Kingdom moved its testing programme in 1957 to Pacific islands under British control, where it conducted further atmospheric nuclear tests, including hydrogen bomb trials.

France conducted 14 nuclear tests in Algeria between 1960 and 1966. During the early years of this period, Algeria was still under French colonial rule, gaining independence in 1962. In 1966, following Algerian independence, France moved its nuclear test site to Polynesia in the South Pacific Ocean, to the atolls of Mururoa and Fangataufa. France also detonated a hydrogen bomb in Polynesia in 1968, and other, mainly underground, nuclear tests were carried out there until 1996, when France ended its nuclear testing program, as a result of strong international criticism, and joined the CTBT nuclear test ban treaty.

China has conducted a total of 47 nuclear tests between 1964 and 1996 in the remote Lop Nor desert region. The most powerful nuclear test was the detonation of a four-megaton nuclear bomb in 1976.

Nuclear tests were banned by the Comprehensive Test Ban Treaty (CTBT) in 1996. It has been signed by 187 countries, but the United States, Russia, China, Israel, Iran, and Egypt have not yet ratified it, so the treaty is not officially in force. However, the CTBT treaty has almost brought nuclear tests to an end. Despite this, nuclear tests have been carried out by India and Pakistan (in the 1990s), and North Korea (in the 2000s), but they have not signed the treaty. Israel has never admitted to conducting a nuclear test. China has begun to strengthen its nuclear deterrence and expand its nuclear arsenal, and as part of this project, it has also been suspected of conducting secret nuclear tests.