Tsar Bomba, the nickname for the AN602 H-bomb, was the largest, most powerful nuclear weapon ever used. It was originally tested by the Soviet Union on October 30, 1961. It was a three stage H-bomb.
This bomb is also called the Father of Bombs.
The explosion had a power of 56,000,000 tonns of TNT (56 Megatons). The Tsar Bomb was actually designed as a 100 Megatonn-Bomb. But as there were problems to detonate a bomb as strong as 100,000,000 tonns of TNT, the Soviet Union technicians reduced its power to 56 Megatonns.