A nitrogen-containing compound which improves emission efficiency, and an organic electroluminescence device including the same are provided. The nitrogen-containing compound according to the present disclosure is represented by Formula 1: When the nitrogen-containing compound has an appropriate or suitable cyclic molecular structure, a small ΔEST value may be obtained, and an organic electroluminescence device including the nitrogen-containing compound in the emission layer may exhibit thermally activated delayed fluorescence emission and have improved external quantum efficiency.