<p>The structure, electronic and magnetic properties of the orthorhombic Cmc2₁ phase of CrO₂ (Cmc2₁ CrO₂) at 105&#xa0;GPa are extensively studied for the first time using first-principles electronic structure computations. The variations in Cr–O distances and &lt; O–Cr–O angles within the CrO₆ octahedra and the formation of two kinds of Cr-four-chain columns result in structural distortion in Cmc2₁ CrO₂. The formation of O-dimers substantially reduces the symmetry of the Cmc2₁ CrO₂ crystal. The system exhibits metallic and nonmagnetic behaviour in the absence of U (U = 0&#xa0;eV). The metallic behaviour is attributed to the partial filling of the Cr-d_3z²_- _r², d_xz, d_yz, d_x²_- _y² and d_xy states, as well as the partial filling of the O-p_x, p_y and p_z states. The system encounters metal–insulator transition (MIT) upon applying U = 3&#xa0;eV, preserving nonmagnetism. The introduction of U = 3&#xa0;eV induces correlation among the Cr-3d electrons, which further splits the Cr-d_3z²_- _r², d_xz, d_yz, d_x²_- _y², d_xy states along with the O-p_x, p_y, p_z states into occupied and unoccupied components, implying complete orbital ordering (OO) among the Cr-3d, as well as among the O-2p states. Consequently, MIT in Cmc2₁ CrO₂ is driven by the simultaneous effect of the&#xa0;structural distortion, reduction in crystal symmetry and correlation-induced OO among the Cr-3d/O-2p states. The nonmagnetism is principally facilitated due to the equal distribution (opposite orientations) of Cr-3d electrons in the two spin channels for both the metallic and insulating states of Cmc2₁ CrO₂.</p>