Energy storage is key to integrating renewable power. Superconducting magnetic energy storage (SMES) systems store power in the magnetic field in a superconducting coil. Once the coil is charged, the current will not stop and the energy can in theory be stored indefinitely. The round-trip efficiency can be greater than 95%, but energy is needed for the cooling of the superconducting coil, and the material is expensive. So far, SMES systems are primarily used for improving power quality through short time storage, but research is going into further applications. This concise treatise provides a hands-on overview of SMES technology. Chapters cover principles, control techniques, use of SMES to improve power quality and transient stability, as well as use of AI with SMES, and address cybersecurity. Case studies underpin the coverage.