Liquid impingement erosion has been known as mechanical degradation, where the original material is removed progressively from a solid surface due to continued exposure to impacts by high-speed liquid droplets. This is a major issue in many industries, including aerospace and aviation and power generation, particularly gas and steam turbines, nuclear power plants, and wind energy. Tremendous numerical and experimental studies have been performed so far to understand the physical phenomena involved in this process and to improve the erosion resistance of different surfaces. In this review paper, first, the liquid–solid impact in a wide range of relative velocities is reviewed fundamentally. Then, the liquid impingement erosion of metals, including damage regimes and damage accumulation mechanisms, as well as the role of solid properties on erosion performance are explained. Finally, promising water droplet erosion-resistant materials and surface treatments are discussed. This review paper is intended to summarize the present knowledge of the different mechanisms involved in the liquid impingement erosion process.