Thermal energy storage using phase change materials (PCMs) is a research topic that has attracted much attention in recent decades. This is mainly due to the potential use of PCMs as latent storage media in a large variety of applications. Although many kinds of PCMs are already commercial products, advanced materials with improved properties and new latent storage concepts are required to better meet the specific requirements of different applications. Moreover, the development of common validation procedures for PCMs is an important issue that should be addressed in order to achieve commercial deployment and implementation of these kinds of materials in latent storage systems. The key subjects addressed on the five papers included in this Special Issue are related to methodologies for material selection, PCM validation and assessment procedures, innovative approaches of PCM applications together with simulation and testing of latent storage prototypes.