<p>Luminescent thermometers have emerged as a powerful tool for monitoring physiological temperature variations that are critical to understanding biological processes and pathological conditions. However, measurement artifacts from instrumental fluctuations and spectral interference from tissue autofluorescence seriously decreased the accuracy and sensitivity of luminescent thermometers. To address these limitations, we developed Zn₂GeO₄:Bi,Tb (ZGO:Bi,Tb) nanoparticles that feature temperature-dependent ratiometric persistent luminescence through a bottom-up synthesis approach for the first time. ZGO:Bi,Tb exhibited temperature-dependent ratiometric persistent luminescence between 298 and 358&#xa0;K. The self-calibration function of ZGO:Bi,Tb allowed the efficient elimination of interference from instrumental anomalies such as photomultiplier voltage fluctuations. Besides, ZGO:Bi,Tb efficiently avoided autofluorescence interference by collecting the ratiometric persistent luminescence after excitation ceases. The temperature quantified by the <i>I</i>₅₄₅/<i>I</i>₅₈₅ ratio of ZGO:Bi,Tb well matched the real temperature with a deviation down to 0.88%. Furthermore, we engineered a theranostic platform with a temperature feedback function by integrating ZGO:Bi,Tb with indocyanine green (ICG), achieving simultaneous photothermal therapy (PTT) and temperature detection. The ZGO:Bi,Tb-ICG platform not only effectively eradicated bacterial pathogens by its photothermal effect but also accurately monitored the temperature during PTT. The PTT temperature determined by the <i>I</i>₅₄₅/<i>I</i>₅₈₅ ratio of the ZGO:Bi,Tb-ICG platform well matched that measured by an infrared thermal camera with a correlation coefficient reaching 0.991. Our study establishes a paradigm for highly accurate and sensitive temperature monitoring and provides a promising tool for research on temperature-dependent physiological processes and pathological states of living organisms.</p> Graphical Abstract <p></p>