The W45 was a multipurpose American nuclear warhead developed in the early 1960s, first built in 1962 and fielded in some applications until 1988. It had a diameter of 11.5 inches (292 mm), a length of 27 inches (686 mm) and weighed 150 pounds (68 kg). The yields of different W45 versions were 0.5, 1, 5, 8, 10, and 15 kilotons. The W45 was designed at the Livermore branch of the University of California Radiation Laboratory (UCRL), now Lawrence Livermore National Laboratory.
The W45 used a common nuclear fission core called the Robin primary, which was used as the fission primary in the thermonuclear W38 and W47 weapons.