Abstract Electronic states of GaN and their ions are studied by employing multi-reference configuration interaction (MRCI) and relativistic DKCCSD(T) calculations. The 3 Σ − state is 532 cm −1 below the 3 Π state using MRCI, whereas the DKCCSD(T)/CBS energy separation is 857 cm −1 . The low lying excited states undergo curve crossing with the dissociative 5 Σ − and 5 Π states causing predissociation. For GaN − , the ground state is 2 Σ + and an electron affinity of 1.44 ± 0.5 eV with an excited 2 Π state at 662 cm −1 . GaN + is weakly bound with an IP of 7.88 eV. The dissociation energy of GaN is 46.5 ± 1 kcal/mol.