Here, the very high thermal sensing capability of Er³⁺,Yb³⁺ doped LaF₃ nanoparticles, where Er³⁺-to-Yb³⁺ energy transfer is used, is reported. Also Pr³⁺,Yb³⁺ doped LaF₃ nanoparticles, with Pr³⁺-to-Yb³⁺ energy transfer, showed temperature sensing in the same temperature regime, but with lower performance. The investigated Er³⁺,Yb³⁺ doped LaF₃ nanoparticles show a remarkably high relative sensitivity S_r of up to 6.6092% K⁻¹ (at 15 K) in the near-infrared (NIR) region, in the cryogenic (15–105 K) temperature region opening a whole new thermometric system suitable for advanced applications in the very low temperature ranges. To date reports on NIR cryogenic sensors have been very scarce.