The W49 was an American thermonuclear warhead, used on the Thor, Atlas, Jupiter, and Titan I ballistic missile systems. W49 warheads were manufactured starting in 1958 and were in service until 1963, with a few warheads being retained until 1975. The W49 has been described as a design derivative of the B28 nuclear bomb nuclear warhead design. It was in diameter and long depending on model, weighing , and had a design yield of 1.44 megatons.