Additive manufacturing (AM) is emerging as a transformative technology for advanced nuclear systems, offering unique capabilities for fabricating complex geometries, tailored material architectures, and multifunctional components beyond the limitations of conventional manufacturing approaches. This Special Issue will highlight recent advances in the application of AM-based technologies in the design and fabrication of protective and functional coatings, advanced materials, and structural components with enhanced mechanical properties and improved resistance to corrosion, oxidation, and irradiation damage for advanced reactors and related nuclear systems. Contributions are welcome on materials development, microstructural characterization, material–process–structure–property relationships, performance evaluation, and qualification, with the goal of accelerating the transition of AM-relevant technologies from laboratory-scale demonstrations toward safer, qualified, and deployable nuclear components.