Tsar Bomba (Russian: Царь-бомба) is the nickname for the AN602 hydrogen bomb, the most powerful nuclear weapon ever detonated. Also referenced as Kuz'kina Mat (Russian: Кузькина мать, Kuzka's mother), in this usage meaning "something that has not been seen before".
Developed by the Soviet Union, the bomb was originally designed to have a yield of about 100 megatons of TNT (420 PJ); however, the bomb yield was reduced to 50 megatons in order to reduce nuclear fallout. This attempt was successful, as it was one of the cleanest (relative to its yield) nuclear bombs ever detonated. Only one bomb of this type was ever built and it was tested on October 30, 1961, in the Novaya Zemlya archipelago.