Lutetium nitride (LuN), an end member of a new quaternary system Si3N4–SiO2–Lu2O3–LuN, was synthesized by direct nitridation of a lutetium metal. The nitridation extent of the lutetium ingot (10 × 5 × 2 mm) reached about 97% by heating at 1600 °C for 8 h with an applied N2 pressure of 0.92 MPa; the initial shape of the bulk metal was maintained in the course of nitridation. The resulting nitrided lutetium possessed a moderately low oxygen content (∼0.7 wt%), which enables the preparation of uncharacterized high nitrogen-containing phases in the Lu–Si–O–N system.