<p>Halide perovskites have attracted significant attention due to their remarkable physical properties and tunable chemistry, making them promising candidates for multifunctional applications. In this work, we systematically investigate the structural, electronic, mechanical, optical, and hydrogen storage properties of the inorganic halide perovskites CsBaX₃ (X = F, Cl, Br, I) using density functional theory (DFT). All compounds crystallize in a stable cubic phase, confirmed by XRD simulations, with CsBaI₃ exhibiting the largest lattice constant among them. The mechanical and chemical stability of these materials further supports their potential applicability. Electronic structure calculations reveal wide band gaps (5.23, 4.67, 4.02, and 3.52 eV), indicating insulator and semiconductor behavior, while the effective mass ratios are higher than one, and charge distribution analyses highlight their suitability for optoelectronic devices. Optical analyses reveal strong absorption in the ultraviolet region, underscoring their potential for UV-photonic applications. Additionally, we evaluate the hydrogen storage potential of CsBaH₃ hydride by replacment of halides. The calculated gravimetric and volumetric hydrogen storage capacities are 1.106 wt% and 70.11 kg H₂.m⁻³, respectively, with a desorption temperature of 364.7 K. These findings suggest that CsBaH₃ hydride is a promising candidate for solid-state hydrogen storage, complementing the optoelectronic functionality of its halide counterparts.</p> Graphical Abstract <p></p>