Recently the new family of spinel-structured nitrides and oxynitrides of group 14 elements (Si, Ge, Sn) has been explored using high-pressure synthesis techniques. The solid-state compounds have high hardness, and they are semiconducting materials that are predicted to have a wide direct band gap. Here we have prepared the corresponding gallium oxynitride spinel with ideal formula Ga3O3N. The synthesis conditions and stability of the new phase were predicted using first-principles calculations, and the experimental study was realized using a combination of laser-heated diamond anvil cell and multianvil high-pressure, high-temperature synthesis techniques. Chemical analysis and X-ray structure refinement indicate that the new phase contains vacancies on the octahedrally coordinated Ga sites, to give an experimental stoichiometry of Ga2.8N0.64O3.24. The Raman spectrum consists of broad bands and resembles the phonon density of states, due to N/O disorder on the anion sites. Optical excitation of the sample with 325 nm laser light at room temperature results in strong photoluminescence between 400 and 750 nm.