There has been a search for new supercapacitor materials that offer superior storage qualities during the past ten years, owing to the needs of the electrochemical energy storage sector. Supercapacitors, which have a higher power density than batteries but a lower energy density, are among the most promising energy storage technologies. Creating innovative materials that increase energy storage efficiency is essential to fulfilling the world's growing energy needs. Recent research has centred on the application of various electrode materials in supercapacitors. This review discusses the parameters of an efficient supercapacitor and the usage of metal oxynitrides as electrode materials. Due to their high cyclability (up to 105 cycles), strong intrinsic conductivity (30000–35000 S cm−1), good wettability, corrosion resistance, and chemical inertness, metal oxynitrides are considered prospective candidates for electrochemical energy storage. This review elaborates on the recent advances in transition metal oxynitrides and compares the properties of transition metal oxynitrides with post-transition and non-transition metal oxynitrides in supercapacitor applications. We envision future paths for this category of energy storage materials in light of this critical study.