Dense plasma is a state of matter and an associated research concept characterized by particle densities significantly higher than those of typical laboratory plasmas or gases, leading to strong inter-particle coupling where potential energy dominates kinetic energy. This field investigates the fundamental physical properties, collective phenomena, and complex dynamics of matter under conditions of extreme density and often high temperature, crucial for understanding astrophysical environments, advancing inertial confinement fusion, and exploring high-energy-density physics.