AbstractBroadband near‐infrared (NIR) emissions in the long wavelength region with simultaneous high efficiency and thermal stability are desirable for NIR phosphor‐converted light‐emitting diodes (NIR pc‐LEDs) light sources. Herein, a novel broadband NIR‐emitting phosphor is reported, Ba₅La₃MgAl₃O₁₅:Cr³⁺ (BLMAO:Cr³⁺), which exhibits a NIR emission band spanning 700–1300 nm with maximum peak wavelength (λ_max) at 925 nm and full width at half maximum of 160 nm. The optimized phosphor achieves an internal quantum efficiency of 66%, and the integrated emission intensity at 423 K remains 61% of that at room temperature, which surpasses most Cr³⁺‐activated phosphors emitting in the long‐wavelength NIR region (λ_max > 900 nm). The NIR luminescence properties are elucidated on the basis of density functional calculations of the multiple Cr³⁺ local structures as generated by the Ba/La occupation disorder in the host material. The applications of the NIR phosphor in pc‐LED devices are demonstrated, showing potential in night‐vision and nondestructive examination. The results indicate that BLMAO:Cr³⁺ is a promising phosphor with highly efficient and thermally stable broadband NIR emission for NIR LED light sources.