The origin of the r-process elements remains the biggest unsolved question in our understanding of chemical evolution in the Milky Way. The most likely astrophysical sites for the formation of these nuclei involve dynamical events in the lives of neutron stars: the inner most regions of massive stars during core collapse supernovae and the merger of a neutron star and another compact object. In both of these environments, nuclear physics plays a paramount role in determining both the evolution of the dense object itself, the properties of neutrinos that are emitted, and what nuclei are synthesized in material that is ejected from the system. In this talk, I will discuss neutrino emission and nucleosynthesis in core collapse supernovae and in neutron star mergers, and some of the theoretical uncertainties that exist in these scenarios.. Astrophysical observables that may give us a direct window into the formation of the r-process elements and the properties of dense matter will also be examined.