The W38 was an American thermonuclear warhead used in the early to mid-1960s as a warhead for Atlas E and F, and LGM-25 Titan IICBMs. It was first built in 1961 and was in service from 1961 to 1965. 70 were deployed on Titan I missiles and 110 on Atlas missiles. It used the Avco Mark 4 reentry vehicle.
The W38 was 32 inches (81 cm) in diameter and 82.5 inches (2 m) long. It weighed 3,080 pounds and had a design yield of 3.75 megatons.