We herein demonstrate the feasibility of employing strontium molybdate as host matrix for trivalent erbium ions for the developing of an optical temperature sensor operating in a wide temperature range suitable for industrial applications. This class of metal molybdate, known for its chemical and thermal capabilities, works as primary luminescent thermometer, relying on the thermally coupled levels of Er3+ arising from downshifting processes, neglecting first, the requirement of calibration curve acquisition and second, the excitation induced heating on the sample typically observed in upconverting luminescent thermometers. The synthesised primary optical thermometer displays a maximum temperature relative sensitivity of 1.13 %. K−1 and minimum temperature uncertainty and 0.09 K. These values make the performance of the Er3+-doped strontium molybdate as optical temperature sensor competitive with the existing luminescent primary thermometers, including a wide operating temperature range up to 413 K and high accuracy as main features. Moreover, it can be easily scaled up and produced due to straightforwardness and cost-effectiveness of the ceramic synthesis method, matching the requirements for its usage in industrial environments.