We report on the observation by electron spin resonance of P-related point defects in nm-thick HfO2 films on (100)Si-an oxide prominent in current high-K insulator research. Based on the principal g matrices and hyperfine tensors inferred from consistent K and Q-band spectra simulations and comparison with established P-associated defects in silica, the center is assigned to a P-2-type defect -a P substituting a Hf atom. The center is observed in the monoclinic phase of the HfO2 oxide with the impaired electron strongly localized on the P atom. Within the concern about dopant penetration out of Si into the high-K layers on top, identification of the dopant-associated defects in the latter appears crucial to which the present basic results provide fundamental access. The centers may operate as detrimental charge trapping sites.