The ability to reversibly control the luminescent properties of functional materials with diverse external stimuli, such as an electric field, strain, and temperature, is crucial for designing high-performance optical devices. Here, we demonstrate that a purely mechanical strain in a flexible mica substrate triggered by bending can be used to dramatically modify the photoluminescence response of a Pr-doped Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 epitaxial thin film in a stable and repeatable manner with a large gauge factor of up to 6853. The strong dependence of the photoluminescence performance on the mechanical bending arises from strain-induced variations in the lattice symmetry of the host film and the local crystal field around the Pr 3+. In particular, because of the nature of mica, the film structure exhibits excellent antifatigue characteristics after 10 4 bending cycles as well as high optical transparency in the range of 450-780 nm. This study provides a viable route for exploring the correlation between structural symmetry and photoluminescence in ferroelectric thin-film systems and offers new possibilities for developing allinorganic, reconfigurable, transparent and flexible light sources, photodetectors, and wearable sensors. 17 , multiferroic BiFeO 3-CoFe 2 O 4 18 , metallic