In this Special Issue, three of the published papers are related to reconfigurable antennas and their applications for wireless communications. The first paper presents a reconfigurable wideband monopole antenna for cognitive radio and wireless applications (contribution 6). The reconfigurability was achieved by four varactor diodes embedded in the band pass filter (BPF) structure, which was integrated with the suggested antenna through its feed line. The simulated impedance characteristics coped with the measured characteristics after fabricating the suggested model with/without the reconfigurable BPF. Furthermore, the model achieved the desired radiation characteristics in terms of radiation pattern with acceptable gain values at the selected frequencies within the achieved frequency range (1.3-3 GHz). The second paper presents a novel antenna structure constructed from cascading multi-stage metamaterial (MTM) unit cells-based printed monopole antenna for 5G mobile communication networks (contribution 7). The proposed antenna is constructed from a printed conductive trace that fetches four MTM unit cells through four T-Resonators (TR) structures. Such a combination is introduced to enhance the antenna gain-bandwidth products at sub-6 GHz bands after exiting the antenna with a coplanar waveguide (CPW) feed. The antenna circuitry is fabricated by etching a copper layer that is mounted on a Taconic RF-43 substrate and has an effective area of 51 \(\times\) 24 mm\({}^{2}\). The proposed antenna provides an acceptable matching impedance with S11 \(\leq\) \(-\)10 dB at 3.7 GHz, 4.6 GHz, 5.2 GHz, and 5.9 GHz. The antenna radiation patterns are evaluated at the frequency bands of interest with a gain average of 9.1-11.6 dBi. Moreover, four optical switches based on LDR resistors are applied to control the antenna gain at 5.85 GHz, which is found to vary from 2 dBi to 11.6 dBi after varying the value of the LDR resistance from 700 \(\Omega\) to 0 \(\Omega\), in a descending manner. It has been found that the proposed antenna provides an acceptable bit error rate (BER) with varying the antenna gain in a very acceptable manner in comparison to the ideal performance. Finally, the proposed antenna is fabricated to be tested experimentally in free space and close to the human body for portable applications. Similarly, the third design introduced a reconfigurable MIMO antenna array of a 3D geometry-based solar cell integration that operates at sub-6 GHz for self-power applications in a 5G modern wireless communication network (contribution 5). The antenna radiation patterns are controlled with two optical switches of Light-Dependent Resistors (LDRs). Two published papers in this Special Issue have discussed dielectric resonator antennas (DRAs) to achieve circular polarization behavior. The first design discussed a wide dual-band circularly polarized (CP) operation for deployment in indoor radio links and INSAT applications (contribution 8). The metasurface and DRs are hosted above a grounded substrate, which is fed through a single coaxial feed placed at a specific angle, employing a modified upper probe of the coaxial fee to enhance the antenna performance. The proposed hybrid technique utilizes the combined benefits of the feed angle and a well-matched metasurface, resulting in performance improvements. Notably, a measured impedance bandwidth of 88.1% for \(\mid\)S11\(\mid\)is achieved within the frequency range of 4.0 GHz to 10.3 GHz. Furthermore, the antenna design exhibits two overlapping, measured at 3 dB axial ratio (AR) bandwidths: 23.62% from 4.25 GHz to 5.4 GHz and 5.12% from 7.6 GHz to 8 GHz. The peak gain of the antenna is measured at 8.4 dBic. The second design presented a novel approach to design a circularly polarized (CP) hemispherical dielectric resonator antenna with a wide axial ratio (AR) bandwidth by incorporating an additional dielectric substrate between the antenna and the ground plane for 5G communication (contribution 9).