High-temperature high-pressure treatment of γ′-Fe 4 N at 1600K and 15GPa in a two-step multi-anvil module integrated in a uniaxial press leads to a phase transition concomitant to a re-crystallization of the nitride material in a hexagonal ɛ-type arrangement. Single crystals of ɛ-Fe 3 N 0.95(2) with a=4.6828(2)Å, c=4.3705(2)Å, V=83.000(6)Å 3 , Z=2) were obtained. A structural model of iron atoms in the motif of a hexagonal close packing with occupation of octahedral voids by nitrogen exhibiting long-range order was constructed and refined on the basis of X-ray diffraction data revealing a nitrogen deficiency x=0.05(2). Two likely structural order models of nitrogen in the space groups P312 (R(F)=0.024, wR(F2)=0.030) and P6 3 22 (R(F)=0.021, wR(F2)=0.023) are discussed. By means of density-functional electronic-structure calculations a pressure-induced phase transition is predicted for Fe 4 N from Pm3¯m to P312 at about 6GPa at 0K, which also offers an interpretation for the reaction mechanism on the basis of the experimental data.