<p>This study presents a comprehensive investigation into the structural, electronic, phonon, and optical properties of the perovskite oxide BaTiO₃ using first-principles calculations based on Density Functional Theory (DFT). Calculations were performed using the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method as implemented in the Wien2k code. Within the Generalized Gradient Approximation (GGA), the computed structural parameters are in high agreement with experimental values, validating the stability of the lattice. We specifically examine the phase transition at approximately 120 ^∘C, where the material shifts from a ferroelectric tetragonal phase to a paraelectric cubic phase. The electronic band structure analysis confirms a semiconducting nature with an indirect band gap; the GGA-calculated value of 1.72&#xa0;eV is analyzed in the context of the well-known derivative underestimation, with density of states (DOS) highlighting the strong hybridization between Ti-3d and O-2p orbitals. To ensure a complete assessment of structural and chemical stability, phonon dispersion and the electron localization function (ELF) were evaluated. Furthermore, frequency-dependent optical properties, including the dielectric function, refractive index, and optical conductivity, were computed. These results underscore the versatility of BaTiO₃ ​for high-performance optoelectronic and dielectric applications, providing a robust theoretical framework for its ferroelectric behavior.</p>