Chicken Interleukin-15 (IL-15) is a cytokine that plays an important role in regulating innate and adaptive immune responses in chickens (Gallus gallus). IL-15 is produced by a variety of cell types, including macrophages, dendritic-like cells, and epithelial cells, in response to infection or inflammatory stimuli. Chicken IL-15 signals through a receptor complex that includes IL-15Rα along with the shared IL-2/15Rβ and common γ chain (γc), activating intracellular signaling pathways such as JAK–STAT that promote lymphocyte proliferation, survival, and activation. In chickens, IL-15 is particularly important for the development and activation of natural killer (NK) cells and cytotoxic CD8⁺ T cells, supporting cellular immune responses against intracellular pathogens. It also contributes to regulation of mucosal immunity in tissues such as the intestinal tract and respiratory system. Chicken IL-15 has been studied in immune responses to important avian pathogens including avian influenza virus, Salmonella spp., and Eimeria species. Due to its role in regulating cytotoxic and mucosal immune responses, chicken IL-15 is widely investigated in poultry immunology and translational research, particularly in studies of vaccine responses, host–pathogen interactions, and strategies to enhance disease resistance in poultry production systems.