Organic electrode materials (OEMs) are now recognized as promising alternatives to inorganic counterparts for the next generation of high-performance and sustainable battery technologies beyond conventional Li-ion batteries. Among the various types of OEMs, carbonyl-containing polymers (CCPs) show the greatest potential to achieve high electrochemical performance at low cost, including high reversible capacity (up to 500 mAh g−1), good cycling stability and excellent rate capability. The cation-independent n-type reaction with moderate redox potential (2.0–3.0 V vs. Li+/Li) gives them the ability to play the role of either cathode or anode, in all kinds of organic batteries (including Li/Na/K/Mg/Zn–organic batteries) using either aprotic or aqueous electrolytes. This chapter provides an overview of CCPs, from the general principles of OEMs, electroactive carbonyl units, and polymerization methods, to electrochemical performance and perspective applications. It is emphasized that precise and cost-effective synthesis, sufficient optimization of electrode and electrolyte, and accurate evaluation of the electrochemical performance are all essential issues for the development of CCPs toward practical use in the future.