With increasing urbanization, railway noise has become a severe environmental problem. At typical rail vehicle speeds (up to 200 km/h), the most important source of noise is rolling noise due to vibration-excitation of the wheels and track as the wheel rolls on the rail. One approach to reducing rolling noise without the addition of costly new components to the railway track is to optimize the properties of the rail pad, which is a compliant cushion inserted between the rails and sleepers as part of the rail fastening system. The main role of the rail pad is to protect the track superstructure (rails, sleepers and ballast), from damage and deterioration. However, it also has a significant impact on rolling noise. Here we present a comprehensive overview of rail pad materials. We first briefly describe the function of rail pads and the general principles of vibration damping and isolation in the elastomeric and viscoelastic polymer-based materials of most relevance to rail pad applications. We then discuss basic design and performance requirements, and materials selection criteria for efficient noise reduction and vibration damping. Finally, we critically evaluate the characteristics of current rail pad materials in the light of these selection criteria and outline promising future materials candidates for the development of novel rail pads with optimized properties.