The nuclear repulsive core and the short-range tensor force are expected to create a high-momentum tail above the Fermi surface of the single-nucleon momentum distribution.  The size and shape of the high-momentum tail have been constrained recently by high-energy electron-nucleus scattering and medium-energy nuclear photodisintegration experiments.  In this talk, we discuss several ramifications of the nucleon high-momentum tail on the equation of state of neutron-rich matter and the reaction dynamics of intermediate-energy heavy-ion collisions.