In recent years, 2D layered semiconductors have received much attention for their potential in next‐generation electronics and optoelectronics. Wide‐bandgap 2D semiconductors are especially important in the blue and ultraviolet wavelength region, although there are very few 2D materials in this region. Here, monolayer β‐type zirconium nitride chloride (β‐ZrNCl) is isolated for the first time, which is an air‐stable layered material with a bandgap of ≈3.0 eV in bulk. Systematical investigation of layer‐dependent Raman scattering of ZrNCl from monolayer, bilayer, to bulk reveals a blueshift of its out‐of‐plane A_1g peak at ≈189 cm^–1. Importantly, this A_1g peak is absent in the monolayer, suggesting that it is a fingerprint to quickly identify the monolayer and for the thickness determination of 2D ZrNCl. The back gate field‐effect transistor based on few‐layer ZrNCl shows a high on/off ratio of 10⁸. These results suggest the potential of 2D β‐ZrNCl for electronic applications.