The influence of the mechanical activation of oxides M2O3 (La2O3, Ce2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Yb2O3, and Lu2O3) on electrical conductivity (æ) of the B2O3-M2O3 molten systems is investigated. It is assumed that the majority carriers in these melts can be protons which enter the melts due to the hydration of B2O3. The variation in the magnitude of for various M2O3 contents is explained by the corresponding variation in the structure of structural units as a result of the dissociation of the boron-oxygen groups, which include the OH groups. The activation energy of electrical conductivity in the B2O3-M2O3 melts increases due to the decay of superstructural units [B3O4.5] and B3O3O3/2OH as the temperature increases. The dependence of is found. In the B2O3-La2O3 → B2O3-Lu2O3 melts series, this energy follows the intraseries periodicity, which depends on the stabilization energy of fundamental terms of the ions of rare-earth elements (REE).