Ratiometric luminescence thermometers based on thermally coupled levels provide reliable temperature sensing with predictable calibration. However, requirement of thermal coupling of levels limits possible energy gap between them, and as, a result, leads to a fundamental limitation of relative thermal sensitivity. Development of luminescence thermometers with two active centers could overcome this drawback and obtain sensors with enhanced thermometric characteristics. Here, we suggested two types of dual-center Gd₂O₃:Tb³⁺/Eu³⁺ nanophosphors, namely co-doping and physical mixture, for ratiometric thermometry within temperature range of 123–473 K. Monitoring luminescence intensity ratio between Tb³⁺ and Eu³⁺ bands provides contactless sensing with moderate relative thermal sensitivities (0.53–0.77 % K⁻¹) and sub-degree temperature resolution (0.3–0.6 K) at room temperature. All studied thermometers irrespective to dispersion system type and doping concentration display exceptional relative sensitivity exceeding the theoretical limit of sensors based on thermally-coupled levels at high temperatures. The largest sensitivity was determined to be 5.6 % K⁻¹@473 K for mixed Gd₂O₃:Tb³⁺ 0.01 at. % + Gd₂O₃:Eu³⁺ 0.2 at. % sample.