This article examines critical considerations and design approaches for applications of millimeter wave ceramic antennas and fibers in harsh extremely high temperature environments such as hypersonic vehicles where the vehicle surface temperatures exceed 1000°C. Ceramic materials with characteristic low loss tangents and high dielectric constants have some significant advantages over polymer fibers and survive extremely high temperature applications. Of the candidate materials, alumina was chosen for ceramic antenna/fiber subsystems for its broadband performance, thermal stability and thermal isolation, and a variety of proofs of concept are presented that demonstrate superior performance and the great potential for use in extremely high temperature applications.