β-Ga₂O₃ combines solar-blind spectral selectivity, intrinsic crystallographic anisotropy, and ultrawide-bandgap robustness, making it a distinctive platform for ultraviolet polarization photodetection. This review examines how microscopic anisotropy is translated into usable polarization information across the material-device-system hierarchy. We first distinguish anisotropic optical absorption, the monoclinic dielectric tensor, excitonic effects, and direction-dependent carrier transport, emphasizing that these mechanisms are related but not interchangeable. We then assess substrate orientation, strain, doping/alloying, and structural engineering as routes to preserve, reshape, amplify, or introduce polarization selectivity. At the device level, responsivity, detectivity, polarization ratio, response speed, and operating bias are evaluated together with self-powered interface engineering and linear-polarimetric reconstruction, highlighting performance trade-offs and the possibility that interfaces may preserve, amplify, or obscure intrinsic anisotropy. Representative proof-of-concept demonstrations in optical communication, neuromorphic processing, physical unclonable functions, and wavelength-assisted molecular sensing are critically assessed from a system-level perspective. We conclude that future progress depends on establishing quantitative links among microscopic anisotropy, external modulation, interfaces, device readout, and polarization-information fidelity rather than pursuing isolated record metrics.