As of 2014, nine countries — the United States, Russia, the United Kingdom, France, China, India, Pakistan, Israel and North Korea — have nuclear arsenals. Together, they maintain a combined stockpile of roughly 16,300 nuclear devices, according to Business Insider.
The United States was the first country to develop nuclear technology, in 1945, followed closely by the Soviet Union and United Kingdom. France and China acquired nuclear weapons during the 1960s. India detonated the "Smiling Buddha" bomb in 1974, and Pakistan tested its first warhead in 1998. North Korea was the last in this group to build and test a nuclear bomb, finally doing so in 2006. It is not known when Israel first developed nuclear weapons, but it is believed to have occurred as early as 1967, but no later than 1979, according to Wikipedia. As of 2014, Israel has never officially acknowledged or denied the existence of such weapons in its arsenal.
Some nations, such as Germany, Turkey and Belgium, have no nuclear weapons of their own design but are in possession of U.S.-made warheads that can be activated only with the authorization of the United States. Some nations, such as Japan and South Africa, are regarded as "paranuclear," as they are technically capable of developing nuclear weapons but have either not developed or abandoned their domestic programs.