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This study investigates the ground-state energetics and thermodynamics of intrinsic point defects in zinc phosphide Zn P using \emph{ab initio} density functional theory combined with an extensive potential energy landscape search. Our analysis reveals that the defect chemistry is dominated by zinc vacancies and zinc interstitials Zn , with equilibrium concentrations significantly surpassing those of other intrinsic species. Notably, we find that phosphorus interstitials P , previously suggested to be significant, possess high formation energies and likely exist only in negligible quantities. The characteristic -type conductivity of undoped Zn P is shown to be a direct consequence of zinc vacancies, which act as shallow acceptors and pull the Fermi level toward the valence band. Furthermore, we identify a positive binding energy between and Zn , leading to the formation of electrically benign Frenkel pairs that partially compensate the intrinsic p-type conductivity. Our results suggest that achieving -type conductivity is fundamentally limited by these thermodynamic constraints. We conclude that hole densities can be optimized through phosphorus-rich growth conditions and high-temperature annealing, and suggest that future photovoltaic strategies should prioritize interface engineering over bulk -type doping.