Bipolar membranes (BPMs) are ion-conductive polymers composed of two layers with fixed charges, often with a catalyst layer between them. They enable control of ion concentrations and fluxes in electrochemical cells, making them suitable for various applications. The chemistry, structure, and physics of BPMs are related to thermodynamics, transport phenomena, and chemical kinetics, which dictate ion and species fluxes and selectivity. These interactions result in emergent structure-property-performance relationships that guide the development of advanced BPMs. The performance trade-offs for BPMs are discussed in the context of emerging applications in energy conversion or storage, and environmental remediation. The review covers the chemical and physical properties of ion-conducting polymers, including the role of ionomer thickness, ion exchange capacity (IEC), and solvent uptake. It also discusses the governing physics of BPMs, such as thermodynamics, species transport, reaction kinetics, and catalysis. The structure-property-performance relationships are explored, highlighting the trade-offs between throughput and selectivity. The applications of BPMs in water electrolysis, CO₂ reduction, energy storage, and environmental remediation are detailed, including their advantages over traditional systems. Challenges and opportunities in BPM development are addressed, emphasizing the need for advanced interfacial catalysts and engineering approaches to optimize BPM systems. The review concludes with an outlook on the potential for chemical-engineering insights to improve the durability, performance, and scale of BPM systems.Bipolar membranes (BPMs) are ion-conductive polymers composed of two layers with fixed charges, often with a catalyst layer between them. They enable control of ion concentrations and fluxes in electrochemical cells, making them suitable for various applications. The chemistry, structure, and physics of BPMs are related to thermodynamics, transport phenomena, and chemical kinetics, which dictate ion and species fluxes and selectivity. These interactions result in emergent structure-property-performance relationships that guide the development of advanced BPMs. The performance trade-offs for BPMs are discussed in the context of emerging applications in energy conversion or storage, and environmental remediation. The review covers the chemical and physical properties of ion-conducting polymers, including the role of ionomer thickness, ion exchange capacity (IEC), and solvent uptake. It also discusses the governing physics of BPMs, such as thermodynamics, species transport, reaction kinetics, and catalysis. The structure-property-performance relationships are explored, highlighting the trade-offs between throughput and selectivity. The applications of BPMs in water electrolysis, CO₂ reduction, energy storage, and environmental remediation are detailed, including their advantages over traditional systems. Challenges and opportunities in BPM development are addressed, emphasizing the need for advanced interfacial catalysts and engineering approaches to optimize BPM systems. The review concludes with an outlook on the potential for chemical-engineering insights to improve the durability, performance, and scale of BPM systems.