The inability to measure pressure with accuracy at high temperature has been a hindrance to the development of simultaneous high‐temperature, high‐pressure experimental techniques. The results of recent laser‐induced fluorescence studies at high temperature and high pressure indicate that Sm:YAG is a promising pressure calibrant with very low‐temperature sensitivity. The most intense feature in the fluorescence spectrum is a doublet at 16186.5 cm−1. The Sm:YAG doublet exhibits a pressure‐induced peak shift comparable to theR1shift of ruby. However, the temperature‐induced shift of the doublet is almost two orders of magnitude less than that observed for theR1peak. Simultaneous high‐pressure‐temperature experiments indicate that the pressure and temperature effects on the frequency and line shape can be added linearly. An empirical model based on the linear combination of pressure dependent frequency shift and temperature dependent linewidth and intensity ratio successfully predicts the doublet line shape at simultaneous pressure and temperature. Use of the model facilitates measurement of peak position at high temperature resulting in improved accuracy and repeatability of the pressure determination. Pressure measurements at 400 °C and 40 kbar based on the Sm:YAG doublet peak position agree with the temperature‐corrected rubyR1pressure measurement to within 3 kbar. At 15 kbar and 900 °C the uncertainty in the Sm:YAG fluorescence peak wavelength is 5 cm−1due to temperature‐induced line broadening; this corresponds to an uncertainty in the pressure determination of ±2.5 kbar. The high thermal and chemical stability of YAG materials make Sm:YAG an ideal pressure calibrant for high‐temperature applications. In addition the frequency and intensity of the Sm:YAG fluorescence allow simple conversion from experimental setups designed for ruby fluorescence measurement.