Calcium-magnesium-alumino-silicates (CMAS) corrosion in thermal barrier coatings (TBCs) is becoming more serious with increasing operation temperature of turbine engines. Here, we report an equimolar YO 1.5 and TaO 2.5 co-doped ZrO 2 (Zr 0.66 Y 0.17 Ta 0.17 O 2 , ZYTO) as a potential CMAS-resistant material for TBCs, which shows a significantly enhanced CMAS resistance than the conventional 17 mol% YO 1.5-stabilized ZrO 2 (17YSZ). After exposure at 1300°C for 100 hours, the CMAS infiltration depth in ZYTO bulk is ~80 μm (for a 20 mg/cm 2 CMAS deposition), in contrast to ~700 μm in 17YSZ bulk (50 hours). Compositional and morphological analyses on the CMAS reaction zone reveal that the excellent CMAS resistance of ZYTO originates from the uniform corrosion through grain and grain boundary, along with densification of the reaction layer. The high CMAS infiltration rate of 17YSZ is attributed to the severe dissolution and infiltration through grain boundary. The reaction mechanisms of CMAS with ZYTO and 17YSZ bulks are discussed and a strategy of enhancing the CMAS resistance is proposed for ZrO 2-based TBC materials. K E Y W O R D S calcium-magnesium-alumino-silicates, phase equilibrium, thermal barrier coatings, zirconia | 1133