Symmetry analysis is carried out for the ordered phases of cubic monoxide TiOy with relative oxygen contents y < 1 and y > 1. It is established that a partially ordered orthorhombic phase (space group Immm)—a derivative of the orthorhombic M3X2h superstructure (at y < 1.0) or the inverse superstructure M2jX3 (at y > 1)—may arise in TiOy . The distribution of Ti and O atoms, oxygen vacancies h, and titanium vacancies j in unit cells of the orthorhombic ordered phases is determined. The phases are formed through the order–disorder transition channel along two rays of a non-Lifshitz star {k4}, and the ordering proceeds as a first-order phase transition. The distribution functions of Ti atoms over the sites of metallic and O atoms over the sites of nonmetallic sublattices are calculated for the orthorhombic superstructures of cubic titanium monoxide TiOy.