The B-41 was a thermonuclear weapon deployed by the United States Strategic Air Command in the early 1960s. It was the most powerful nuclear bomb ever developed by the United States, with a maximum yield of 25 megatons of TNT. A top secret document, states “The US has stockpiled bombs of 9 MT and 23 MT...” which would likely be referring to the B-41's actual yield(s). The B-41 was the only three-stage thermonuclear weapon fielded by the U.S.

A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lower mass, or a combination of these benefits. Characteristics of nuclear fusion reactions make possible the use of non-fissile depleted uranium as the weapon's main fuel, thus allowing more efficient use of scarce fissile material such as uranium-235 or plutonium-239. The first full-scale thermonuclear test was carried out by the United States in 1952 and the concept has since been employed by most of the world's nuclear powers in the design of their weapons.