The resistivity and Hall coefficientRHfor Zn‐doped GaP were measured at temperatures between 4.2° and 775°K. Neutron activation and through diffusion with radioactive65Zn were used to determine the Zn concentrationNZn, which ranged from 6.7×1016cm−3to 2.1×1019cm−3. At the lowest Zn concentration the thermal ionization energy for Zn in GaP was found to be 0.060±0.002 eV. The thermal ionization energy decreases rapidly for Zn concentrations in excess of 2.0×1017cm−3. Metallic impurity conduction was observed at a Zn concentration of 2.1×1019cm−3. The low‐concentration region is observed forNZn≲2.0×1017 cm−3, the intermediate‐concentration region for2.0×1017≲NZn≲2.1×1019 cm−3, and the high‐concentration region forNZn≳2.1×1019 cm−3. In the intermediate‐concentration region the high‐temperature hole concentration, determined fromp=1/eRH, was found to exceed the Zn concentration by a significant amount. Analysis of the temperature‐dependent hole concentration results in an effective density‐of‐states mass ratio of approximately 0.5. The lightest doped sample had a room‐temperature Hall mobility of 120 cm2/V·sec and a maximum mobility of 2050 cm2/V·sec at 55°K. The maximum mobility at low temperature is limited by ionized and neutral impurity scattering, while the dominant high‐temperature scattering mechanism appears to be optical phonon scattering.