The electrical conductivity (σ) was measured for a single crystal of San Carlos olivine (Fo89.1) for all three principal orientations over oxygen fugacities 10-7 < fO2 < 101 Pa at 1100, 1200, and 1300¿C. Fe-doped Pt electrodes were used in conjunction with a conservative range of fO2, T, and time to reduce Fe loss resulting in data that is ~0.15 log units higher in conductivity than previous studies. At 1200¿C and fO2 = 10-1 Pa, σ<100> = 10-2.27S/m, σ<010> = 10-2.49S/m, σ<001> = 10-2.40S/m. The dependences of σ on T and fO2 have been simultaneously modeled with undifferentiated mixed conduction of small polarons and Mg vacancies to obtain steady-state fO2-independent activation energies: Ea<100> = 0.32 eV, Ea<010> = 0.56 eV, Ea<001> = 0.71 eV. A single crystal of dry olivine would provide a maximum of ~100.4 S/m azimuthal σ contrast for T < 1500¿C. The anisotropic results are combined to create an isotropic model with Ea = 0.53 eV.