Abstract: With the great explosion of wireless systems and their applications and also with the limited enabling energy and spectrum resources available, it becomes more and more crucial to focus on the reduction of energy use in future wireless systems. The most efficient way of electromagnetic wave energy reception is to fully capture the two orthogonal components of its field vector in connection with polarization diversity. This paper shows how to exploit the concept of polarization diversity over the millimeter-wave (mmW) frequency band which has been assigned for wireless applications. This is done by developing the theory of operation and design procedure of dually-polarized mmW components. The novelty presented in this paper lies in developing a principle of operation so to come up with a class of dually-polarized mmW components, namely, 3-dB couplers, 0-dB couplers, and phase shifters. This allows the development of dually-polarized beamforming networks such as Butler matrix. A full analytical design procedure is presented with verification through full-wave simulations and prototype measurements.