This Special Issue, "Advanced Studies on High-Performance Metal-Ion Capacitors: Technologies, Systems and Applications", highlights recent progress in hybrid electrochemical energy storage systems that integrate the merits of both batteries and supercapacitors. This Special Issue brings together research articles and reviews that address the challenges involved in the construction of metal-ion capacitors from multiple perspectives, including electrode structure engineering, heteroatom doping, electrolyte design and innovative cell configurations. This Reprint provides a comprehensive overview of emerging technologies and future directions for metal-ion capacitors, offering valuable insights for designing next-generation high-performance and sustainable electrochemical energy storage systems.