Searching for a material that simultaneously satisfies highly conductive and corrosion-stable properties is crucial for various energy conversion applications, particularly for catalyst-supporting materials in polymer electrolyte membrane fuel cells (PEMFC). Here, we suggest the Mg-Ti-O chemical space as promising ternary compounds with high electrical conductivity and corrosion stability in acidic conditions to be potentially used in such applications. A high electrical conductivity (6.09 × 10^-1 S/cm) and a good corrosion stability (1.2 × 10^-4 mA cm^-2 at pH = 1) are achieved at room temperature, by tuning the chemical compositions of Mg_1-xTi_2+xO₅ (MTO). We found that the corrosion stability of suggested MTO is two orders of magnitude higher than that of conventional carbon supporters used for PEMFC while providing high electrical conductivity. Furthermore, our combined computational and experimental works elucidate that the reducing gas environment during the solid-state synthesis ensures the higher Ti solubility in MTO, i.e., a reduced valence state of Ti, thus promoted the electrical conduction.