High-temperature shape memory alloys (HTSMAs) are a class of developed functional materials that exhibit the distinctive thermoelastic martensitic transformation behavior of conventional shape memory alloys (SMAs) while showing stability at high temperatures. Their potential to regain large strains, give high actuation forces, and keep functionality in harsh environments makes them capable for challenging applications in automotive, aerospace, sensors, actuators, energy, and biomedical systems. This chapter provides an extensive overview of HTSMAs, covering their basic thermomechanical principles, alloy systems, processing techniques, and important performance attributes such as martensite and austenite transformation temperatures, mechanical properties, and environmental stability. Special concentration is given to Ti-Ni-based SMAs with the addition of noble and refractory elements, which remain the most broadly studied systems for high-temperature applications. Emerging tendencies such as 4D printing, additive manufacturing, and integration with artificial intelligence are also discussed, representing the importance of HTSMAs in next-generation skillful structures and smart devices. In general, this chapter highlights both the opportunities and the ongoing issues, including long-term durability, cost, and resistance to oxidation, that keep the future research and application of HTSMAs.