In this study, we provide the critical electric field and dielectric strength of cryogenic gas mixtures over an extended cryogenic temperature and pressure range that covers most of the operating conditions of superconducting applications. For gas-cooled cryogenic systems, condensation must not occur during operation. To prevent condensation, we determine the maximum allowed mole fractions of gas species consisting cryogenic gas mixtures by accounting for the operating conditions of cryogenic applications. Subsequently, we estimate the dielectric strength of the gas mixtures in terms of the density-reduced critical electric field ((E/N)cr), obtained by solving the Boltzmann equation with the two-term approximation method. Using the values of (E/N)cr, we calculate the critical electric field (Ecr) over the extended cryogenic operation range of 10–100 K at pressures between 1.0 and 2.0 MPa. The results show that the dielectric strength of cryogenic gas mixtures varies as a function of temperature at a constant operating pressure and reaches its minimum at the condensation point of each gas mixture. The results also suggest that (E/N)cr cannot accurately represent the maximum achievable dielectric strength of a gas mixture unless the maximum allowed mole fractions of gas species have been taken into account. Hence, we discuss (E/N)cr values that are derived from the regulated concentration of gas constituents, which will prevent the components of gas mixtures from condensing. This study provides useful recommendations on the suitability of the gas mixtures and useful reference data for the dielectric design of superconducting and cryogenic applications.