Abstract:The particle nature of dark matter is a driving question of contemporary physics, with astrophysical experiments leading the search for dark matter annihilation or decay signatures. In an era of ever-tightening constraints on Weakly-interacting massive particles (WIMPs), there is increasing interest in light (<1 GeV) dark matter candidates. Sterile neutrinos, which could provide an elegant solution to the puzzle of the observed active neutrino masses and mixing, are among the most well-motivated light dark matter candidates, with astrophysical X-ray observations offering the best opportunity for discovery. In this talk, I will review the status of X-ray searches for sterile neutrinos, including the candidate sterile neutrino signal at ~3.5 keV. In particular, I will describe the novel use of the NuSTAR X-ray satellite observatory to provide the leading constraints in much of the mass range ~10-50 keV, improving upon previous limits at some masses by over an order of magnitude and reducing the available parameter space for sterile neutrinos in the simplest models by almost two-thirds. Finally, I will describe how NuSTAR may help us definitively probe the simplest sterile neutrino dark matter models in the coming years.