Abstract Glasses with ultra‐wideband near‐infrared emission and superior irradiation resistance are important for the potential applications in optical communications under harsh environments. Here, transparent 35La 2 O 3 ‐(65‐ x )Ga 2 O 3 ‐ x Ta 2 O 5 (LGT) and Er 3+ /Tm 3+ /Pr 3+ tri‐doped LGT glasses are fabricated using the levitation method. LGT glasses exhibit a wide glass‐formation region, low largest vibration energy, high refractive indices, and excellent mechanical properties. Additionally, Er 3+ /Tm 3+ /Pr 3+ tri‐doped LGT samples with varying Pr 3+ contents are characterized by possessing good thermal stability ( T g >849°C), wide transparent optical window, strong radiation resistance, excellent compatibility between low wavelength dispersion ( v d >31.2), and large refractive index ( n d >2.048). By optimizing the doping content of Er 3+ , Tm 3+ , and Pr 3+ in an appropriate ratio, the ultra‐wideband near‐infrared luminescence ranging from 1250 to 1640 nm (FWHM = 251 nm) has been acquired under 808 nm pumping. Furthermore, decay curves are measured to reveal the fluorescence dynamics, and then the related emission mechanism is elaborated systematically. Meanwhile, the effects of gamma irradiation doses on microstructure, transmittance spectra, and fluorescence characteristics are studied. This work may offer a valuable reference for doping optimization and new design strategy of multifunctional materials.