Abstract: Ammonia is an essential chemical feedstock and a potential carbon-free fuel, offering significant advantages for energy storage and transportation. However, current industrial ammonia production still relies predominantly on the century-old Haber–Bosch process, whose high-temperature and high-pressure operating conditions and heavy dependence on fossil resources result in enormous energy consumption and substantial CO₂ emissions. Consequently, there is an urgent need to develop green ammonia synthesis technologies that operate under milder conditions. In recent years, chemical looping ammonia synthesis （CLAS） has attracted increasing attention. This process decouples ammonia synthesis into two cyclic steps—nitridation and ammoniation—and employs nitrogen carriers to shuttle active nitrogen species, thereby alleviating the intrinsic thermodynamic–kinetic trade-off of conventional ammonia synthesis. Nitrogen carrier materials are central to CLAS, as they are responsible for nitrogen fixation and transport during the cycle; however, commonly used carriers suffer from limited nitrogen capacity and sluggish kinetics, which constrain CLAS performance. This review categorizes CLAS from the perspectives of hydrogen sources and nitrogen carrier materials and summarizes recent progress in carrier development. It is found that introducing high-entropy nitrogen carriers can effectively overcome the poor reactivity and insufficient nitrogen-carrying capacity of traditional carriers. Nevertheless, the targeted regulation of the complex chemical space arising from multimetal synergy in high-entropy carriers remains highly challenging. The relationships between composition/structure and performance are difficult to capture empirically, and conventional trial-and-error approaches are time-consuming while posing risks of phase separation and ambiguous active sites. Therefore, systematic design principles are urgently required to guide the development of high-entropy nitrogen carriers, balancing stability and activity in multicomponent systems. Looking forward, machine-learning-assisted precise design and regulation strategies for high-entropy nitrogen carriers offer a promising pathway toward the development of high-performance carriers for chemical looping ammonia synthesis.