Batteries have long been a cornerstone of energy storage technologies, offering low-carbon and sustainable solutions across diverse applications from large-scale power grids to electric vehicles and portable electronics. In response to growing global energy demands, research efforts are increasingly directed toward advancing battery chemistries and cell designs to achieve higher performance, efficiency, and scalability. Among emerging systems, potassium–oxygen (K–O2) batteries have attracted significant attention due to their high theoretical energy density (~935 Wh kg-1) and the earth-abundant nature of potassium. This review presents a comprehensive overview of K–O2 battery technology, covering fundamental operating principles, key performance limitations, and persistent challenges. Particular focus is given to critical aspects such as electrode architecture, electrolyte stability, and oxygen-related electrochemistry, which collectively govern cell efficiency and durability. In addition, we highlight recent advancements aimed at overcoming these barriers and provide a critical assessment of the current technological readiness of K–O2 batteries. While the system holds considerable promise, substantial progress is still required to translate laboratory success into practical, real-world applications. Finally, future directions and opportunities for the development and integration of K–O2 batteries are discussed.