This chapter concerns thermal and thermochemical energy conversion and storage with a specific focus on materials. It consists of 6 sections. Section 1 introduces the background and rationales and the structure of this chapter. Section 2 discusses thermochemical materials for energy conversion and chemical production. This is followed by Section 3 on thermochemical based thermal energy storage; Section 4 on materials for low to medium temperature volumetric absorption, storage and conversion of solar energy; and Section 5 on materials for high-temperature solar energy conversion, storage and transfer. Finally, Section 6 concludes this chapter.