Hard, refractory thin films consisting of group IVB element mono-nitrides deposited using various chemical and physical vapour-deposition techniques are widely used in wear-resistant applications. As the demand for performance exceeds the capabilities of existing materials, new materials with superior properties must be developed. Here we report the realization and characterization of hard cubic Zr3N4 (c-Zr3N4) thin films. The films, deposited using a novel but industrially viable modified filtered cathodic arc (FCA) method, undergo a phase transformation from orthorhombic to cubic above a critical stress level of 9 GPa as determined by X-ray diffraction and Raman spectroscopy. The c-Zr3N4 films are significantly harder (similar to 36 GPa) than both the orthorhombic Zr3N4 (o-Zr3N4) and ZrN films (similar to 27 GPa). The ability to deposit this material directly onto components as a thin film will allow its use in wear- and oxidation-resistant applications.