All fluorine atoms in fluoride compounds discussed in this book were synthesized in the stars or in stellar processes well before the solar system was formed some 4.6. billion years ago. The main cosmic production sites are, however, still elusive. This is not only because it is challenging to empirically determine the buildup of fluorine abundance in the universe over time, but also because of the uncertainties in our understanding of the cosmic formation and destruction processes, and the so-called chemical evolution of the element in different stellar populations. In this chapter we present our current knowledge of how the element fluorine is synthesized and why it is important to determine. It turns out that there are three possible formation sites: (1) in the late stages of evolution of sunlike stars, (2) in the neutrino process following the core collapse of massive stars during a supernova explosion of type II, and (3) in very massive stars experiencing a large stellar wind. The only site that has observationally been verified is the first one, but astronomers are still arguing about the possible importance of the other two and about which of the three was the dominant source of the fluorine atoms found on the Earth and in the universe.