Nitrides and oxynitrides exhibit great potential for novel material development, since their electronic structures can be controlled by tuning the amounts of air-abundant nitrogen and oxygen elements therein. However, the above control methods still need to be developed, and the crystal and electronic structures of the produced nitrides/oxynitrides need to be understood. Herein, I summarize the recent progress in nitride and oxynitride synthesis, highlighting novel low-temperature nitridation of oxides by molten NaNH₂, and attempt to rationalize the crystal and electronic structures of nitride and oxynitrides. Moreover, I describe how the catalytic activity of manganese oxynitrides in the oxygen reduction reaction can be enhanced by tuning their nitrogen content and thus their electronic structures.