Around the world, in the deepest mines and the deepest oceans, from the Antarctic to low-Earth orbit, experiments are now searching for the elusive dark matter particle; I will attempt to explain how and why. Many independent strands of astrophysical evidence indicate that roughly 85% of the matter in our universe is "dark matter", a gas of weakly-interacting particles undetected in current accelerators and unaccounted for in the Standard Model of particle physics. The detection and identification of dark matter has proven impossibly difficult in the past. Now, after many decades of diligent work, we may be on the verge of a revolution in this field. In this talk I will review the astrophysical evidence for dark matter, the theoretical candidates for this strange substance, and the instruments and experiments poised to reveal its true nature, thereby opening a new chapter in fundamental physics.