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The Garnet-type solid electrolyte Li₇La₃Zr₂O₁₂ (LLZO) is one of the most promising candidates for solid-state batteries. This study focuses on the cubic-LLZO due to its high ionic

conductivity. The primary goal here is to optimize the ionic conductivity in cubic-LLZO, and one strategy to attain this goal is by performing the native defect analysis of the cubic-LLZO. Density functional theory was employed to calculate defect formation energies for a range of point defects. We use a thermodynamically stable region of cubic-LLZO which can be broadly classified into two categories: O-rich/metal-poor and O-poor/metal-rich conditions. In O-poor conditions, defects such as O vacancies, La and Zr substitutions, and Li interstitials exhibit higher concentrations. Conversely, in O-rich conditions, Li, La, and Zr vacancies have higher concentrations. This work provides a fundamental understanding of the defects, facilitating further investigations into the conduction mechanism of cubic-LLZO under extreme conditions.