The substitution of metal sites in Mg2TiO4 substrate leads to charge imbalance that will be closely related to a variety of changes including lattice structure, cell distortion, and photophysical properties. Herein, the co-substitution strategy of [Ga3+ -Ga3+] for [Mg2+ -Ti4+] and Sn4 + for Ti4 + achieves for the first time the novel Mg3Ga2 SnO8 (MGS):xMn(4+) (x = 0-3%) phosphors with efficient red emissions. In terms of X-ray powder diffraction (XRD) and Rietveld refinement analysis, MGS:Mn4+ possesses a structure isotypic of Mg2TiO4 in the cubic space group Fd (3) over barm (227). There are two types of octahedra for Mn4+ ions in this structure, where Ga3+ ions completely occupy a group of octahedral sites and Mg2+/Sn4 + has been randomly distributed over another group of octahedral sites. A strong excitation band in the broad spectral range (220-550 nm) has been identified, thus facilitating the commercial uses for blue LED chips excitation. An intense red emission band at 680 nm has been observed due to the characteristic E-2(g) -(4)A(2g) transition of Mn4+ ions. A concentration quenching effect occurs when the Mn4+ content exceeds 1.5%, and the quenching mechanism is demonstrated to be dipole-quadrupole interactions. Temperature-dependent luminescence measurements support its good thermal stability, and the corresponding activation energy E-a is determined to be 0.2552 eV. The possible luminous mechanism of the Mn4 + ion is explained by the Tanabe-Sugano energy level diagram. The crystal field strength and the Racah parameters together with the nephelauxetic ratio are also determined for Mn4 + in the MGS lattice. High color rendition warm white-lightemitting diodes (WLEDs) based on the optimal phosphor MGS:1.5%Mn4 +,1.5%Li+ possess a color rendering index and color temperature of 85.6 and 3658 K, respectively. Its feasibility for application in solid-state white lighting has been verified.