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We report for the first time the inscription of retro-reflective Bragg gratings in multimode crystalline sapphire fiber. The gratings were fabricated using 800-nm femtosecond laser radiation and a phase mask. The grating behavior was investigated up to 1500°C with no detectable reduction in the grating reflectivity or hysteresis in the Bragg resonance. Measurements of the change in the effective index of the fiber as a function of temperature are reported and the performance of the grating as a temperature sensor is evaluated.