India’s Department of Atomic Energy (DAE) is responsible for two nuclear programs. First, its civilian energy program involves several nuclear power reactors that supply 2–3 percent of India’s electricity. Second, its military program, based on two research reactors and related reprocessing plants, produces weapons-grade plutonium for India’s strategic nuclear forces. The Cirus reactor, that began operating in 1960, produced plutonium for about two nuclear weapons per year and was shut down in 2010; the Dhruva reactor, operational since 1986, produces plutonium sufficient for about five nuclear weapons annually; and a third research reactor with capabilities similar to Dhruva could be operational in the late 2010s. Thus, by the mid-2010s, these reactors had produced weapons-grade plutonium for an estimated 120–130 nuclear weapons. These weapons are delivered by a force of ballistic missiles, developed by the Defense Research and Development Organization (DRDO). This chapter examines the evolution of India’s nuclear weapons program from the 1940s to the present.