Tsar Bomba was the most powerful nuclear weapon ever detonated.
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.

沙皇炸彈（俄語：Царь-бомба），型號為RDS-220氫彈，代號為「伊凡」­（Иван，Ivan），是在冷戰時期由蘇聯所製造的實驗氫彈，總共製造了兩枚。「沙­皇炸彈」之名即意謂著它是「炸彈之王」，因為它是人類至今所製造過所有種類的炸彈中，­體積，重量和威力上均為最強大的炸彈。

它的爆炸當量（yield）本來相當於1億噸的TNT炸藥，不過蘇聯當局憂心試爆後的­核子落塵對環境的嚴重影響導致內政難題與外交風波，因此將核彈縮減為5000萬噸的爆­炸威力。

儘管被刪減了一半的威力，沙皇炸彈的威力依舊是第二次世界大戰末期投擲於廣島的「小男­孩」原子彈的3846倍。雖然蘇聯成功完成試爆，沙皇炸彈仍然從未列入現役武器，蘇聯­軍方僅僅想要利用沙皇炸彈作為蘇聯在軍力上的象徵與展示。