Matrix isolation experiments have been conducted on the Mg14N, 25Mg14N, Mg15N, and 25Mg15N radicals which were formed by the reaction of a plume of magnesium metal produced with laser ablation and either acetonitrile vapour or nitrogen atoms. The radicals were isolated in an inert neon matrix at 4.3 K and studied with electron spin resonance spectroscopy. The ground electronic state of MgN was determined to be 4Σ-. The following magnetic parameters were determined experimentally for MgN: g⊥ = 2.004 78 (2), g∥ = 2.001 72 (4), |D| = 9797 (6) MHz, A⊥(14N) = 19.7 (2) MHz, A∥ (14N) = -4.0 (3) MHz, A⊥(15N) = 27.5 (3) MHz, A∥ (15N) = -5.7 (3) MHz, A⊥ (25Mg) = -60.7 (5) MHz, and A∥(25Mg) = -65 (3) MHz. The low-lying electronic states of MgN were also investigated using the complete active space multiconfigurational self-consistent field technique. By plotting the potential energy surface, theoretical parameters for the ground state with a configuration of 5σ26σ27σ12π12π1 were able to be determined, including re = 2.090 Å and De = 11.28 kcal/mol.