The phase diagram of the Al2O3-ZrO2-Sm2O3 system was constructed in the temperature range 1250 degrees-2800 degrees C. The phase transformations in the system are completed in eutectic reactions. No ternary compounds or regions of appreciable solid solution were found in the components or binaries in this ternary system. Two new ternary and one new binary eutectics were found. The minimum melting temperature is 1680 degrees C and it corresponds to the ternary eutectic Al2O3+F-ZrO2+SmAlO3. The solidus surface projection, the schematic of the alloy crystallization path, and the vertical sections present the complete phase diagram of the Al2O3-ZrO2-Sm2O3 system.