Nonstoichiometric compounds of Mn 1−δ O were self-propagating high-temperature synthesized by ignition of thoroughly mixed powders of Mn, NaClO 4 , and MnO without additional external heating. The mixing ratio was systematically varied to control δ. Single phase Mn 1−δ O products containing nonstoichiometric defects were obtained for 0<δ≤0.025. With increase in δ, Mn 3 O 4 content of the products is increased. Double phases of Mn 1−δ O and Mn 3 O 4 were obtained at 0.025<δ≤0.150. The lattice parameter, a, of the single phase Mn 1−δ O was well explained by the linear equation: a=−0.0667δ+4.448.