Inorganic cesium lead halide (${\text{CsPbX}}_3$, $\mathrm{X}=\mathrm{Cl}$, Br, I) nanocrystals (NCs) attract extensive attention because of their excellent optoelectronic performance. However, the classic ${\text{CsPbX}}_3$ NCs suffer from toxicity and instability, which impede their further applications in commercial fields. Here the inorganic lead-free cesium copper chlorine NCs are synthesized by a facile hot-injection method. The blue-emission 3D ${\mathrm{CsCu}}_2{\mathrm{Cl}}_3$ and green-emission 0D ${\mathrm{Cs}}_3{\mathrm{Cu}}_2{\mathrm{Cl}}_5$ NCs are prepared at 70°C and 120°C, respectively, suggesting that the reaction temperature may account for the final components. Owing to the self-trapped exciton effect, the unique optical properties, such as high photoluminescence (PL) quantum yield, broadband emission, large Stokes shift, and long PL decay time, are demonstrated for both cesium copper chlorine NCs. Moreover, highly efficient and stable warm white light-emitting diodes are fabricated with ${\mathrm{CsCu}}_2{\mathrm{Cl}}_3$ and ${\mathrm{Cs}}_3{\mathrm{Cu}}_2{\mathrm{Cl}}_5$ NCs. The study highlights the promising potential for lead-free cesium copper chlorine nanocrystals in nontoxic solid-state lighting applications.