Dark-blue sodium nitride, Na3N, was prepared by the reaction of metallic sodium or liquid Na-K alloy with plasma-activated nitrogen at low pressure. The compound crystallizes in the cubic anti-ReO3-type structure (space group Pm3m with a = 4.73301(6) angstrom and Z = 1) according to powder and single-crystal X-ray diffraction data. Na3N decomposes above 104 degrees C into the elements, with Delta H-f estimated at +64(2) kJ/mol.