We provide experimental evidence for an intrinsic defect in GaNP from optically detected magnetic resonance (ODMR). This defect is identified as a P-N complex, exhibiting hyperfine structure due to interactions with a nuclear spin I=12 of one P atom and also a nuclear spin I=1 due to one N atom. The introduction of the defect is assisted by the incorporation of N within the studied N composition range of up to 3.1%, under non-equilibrium growth conditions during gas-source molecular beam epitaxy. The corresponding ODMR spectrum was found to be isotropic, suggesting an A1 symmetry of the defect state. The localization of the electron wave function at the P-N defect in GaNP is found to be even stronger than that for the isolated PGa antisite in its parent binary compound GaP. © 2003 Elsevier B.V. All rights reserved.