This chapter presents the advancement of a millimeter-wave (FSS) absorber with polarization insensitivity and a triple-band feature. The objective of designing this absorber is to reduce the radar cross-section at millimeter-wave frequencies. This absorber achieves noteworthy absorption of 99.92%, 99.48%, and 97.49% at specific frequencies of 20.08 GHz, 25.17 GHz, and 28.11 GHz, respectively, all within the Ku, K, and Ka bands. The absorber consists of a unit cell of three layers, each with a distinct geometric pattern. A copper sheet supports and prints these layers onto a dielectric substrate. The total thickness of the structure is 0.7372 λ0, and the periodicity is 0.05361 λ0. Furthermore, we performed parametric evaluations to adjust the absorption frequencies precisely. The absorber’s polarization remains insensitive to both TE and TM modes. Moreover, we have analyzed the surface currents and electric field distribution to understand the absorption process. The proposed design has great potential for reducing radar cross-sections, shielding against electromagnetic interference, and enabling real-time wireless applications in the millimeter-wave region. The preliminary simulation findings follow our design objectives.