Microwave absorbing nanomaterials (MAMs) have emerged as a critical class of functional materials designed to mitigate electromagnetic interference (EMI), enhance stealth technologies, and enable advanced biomedical and communication applications. 2008 onwards, there is a drastic change in nanomaterials which are linked with wide range of  tailored dielectric and magnetic properties, optimized impedance matching, and multifunctional integration design of absorbers. This review provides a comprehensive overview of the fundamental mechanisms governing microwave absorption, including dielectric loss, magnetic resonance, interfacial polarization, and multiple scatter effects. Particular emphasis is placed on the role of nanostructuring, hybridization, and core shell architectures in enhancing absorption efficiency across broad frequency ranges. Nanomaterials such as graphene, carbon nanotubes, and carbon foams have demonstrated exceptional dielectric loss and tunable conductivity, while magnetic nanoparticles (Fe₃O₄, Co, Ni, ferrites) contribute to magnetic resonance and synergistic effects. Polymer and hybrid nanocomposites further expand the design space, offering lightweight, flexible, and scalable solutions. Fabrication techniques including sol–gel, hydrothermal synthesis, chemical vapor deposition, and melt blending have been refined to achieve reproducibility and industrial relevance. Diverse applications in consumer electronics, stealth coatings in defense, wireless communication devices, and biomedical platforms such as hyperthermia therapy and biosensing. With significant advances, the challenges remain in balancing absorption efficiency with material cost, scalability, and environmental sustainability. By systematically analyzing mechanisms, materials, fabrication strategies, and applications, this review aims to provide a roadmap for the next generation of microwave absorbing nanomaterials.