Abstract: MXenes are a rapidly expanding family of two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides. They have emerged as a prominent class of materials for advanced electrochemical energy storage owing to their metallic conductivity, compositional tunability, and hydrophilic surfaces terminated with functional groups. These unique physicochemical characteristics, combined with solution processability and scalable synthesis, have positioned MXenes as promising electrode materials for next-generation supercapacitors (SCs). SCs store energy through fast and reversible interfacial charge-transfer processes, enabling high power density, long cycle life, and environmentally sustainable energy delivery. Despite significant progress, the practical implementation of MXene-based SCs remains constrained by several intrinsic challenges, including nanosheet restacking that reduces ion-accessible surface area, surface terminations that may be electrochemically inactive and susceptible to oxidation, and pronounced self-discharge behavior arising from rich surface chemistry. This review provides a comprehensive and critical analysis of recent advances in MXene-based SCs aimed at overcoming these limitations, with particular emphasis on interlayer engineering, heterostructure design, and surface termination modulation. By integrating structure-property-performance correlations with a scalability and practical device perspective, this review offers a mechanistic framework for translating fundamental MXene chemistry into deployable, next-generation SC technologies. We first discuss the structural chemistry of MAX phases and MXenes, along with their synthesis strategies. Subsequently, recent advances in MXene-based SC electrodes by linking their structural design to final device performance. Finally, the remaining scientific and technological challenges of MXene-based SCs are highlighted alongside proposed future research directions. Collectively, this review bridges fundamental MXene chemistry with device-level considerations, outlining a rational framework to accelerate the development of practical, scalable MXene-based SCs for next-generation energy storage.