Presented work is devoted to theoretical investigation of possible self-trapped exciton (STE) configuration in corundum crystal. Our study is based on ab initio calculations performed in CRYSTAL09 program package by means of Hartree-Fock and hybrid functional B3LYP (B3LYP40 and B3LYP30) methods. Charge density distribution of presented defect configuration and its geometry relaxation were obtained. Hybrid methods delocalize hole component of STE over two near oxygen atoms in comparative proportion. Orientation of STE in crystal is close to be perpendicular to z -axis, i.e. it lies mainly in horizontal plane. All calculations were carried out using periodic boundary conditions and full relaxation of supercell. STE luminescence energy was found to be 4.96 eV for HF, 5.01 eV for B3LYP40 and 4.84 eV for B3LYP30.