Thermoelectric materials, which could directly convert a temperature gradient into electrical energy, provide a promising solution for sustainable energy harvesting. The development of thermoelectric materials has recently gained tremendous attention in the fields of solid-state physics, chemistry, materials science, and engineering. Many strategies have been implemented to achieve high-efficiency thermoelectric conversion efficiency, e.g., doping, defect, intercalation, band engineering, strain, nanostructures, and molecule junctions, which greatly promote further applications of thermoelectrics. This Special Issue on "Materials Physics in Thermoelectric Materials" aims to provide a unique international forum for researchers working in thermoelectric materials to report their latest endeavors in advancing this field, including new pristine thermoelectric materials, strategies used to improve thermoelectric performance, theoretical understanding of thermoelectrics, physical insights into engineering high-performance thermoelectrics, computational discovery of new thermoelectric materials, and so on.