Chicken Interleukin-1 Receptor Antagonist (IL-1Ra) is an anti-inflammatory cytokine produced by monocytes, macrophages, and other immune cells in chickens (Gallus gallus) that functions as a key regulator of IL-1–mediated inflammation. IL-1Ra competitively binds to the IL-1 receptor (IL-1R1) without initiating downstream signaling, thereby blocking the pro-inflammatory effects of IL-1β and limiting activation of NF-κB and MAPK pathways that drive fever, leukocyte recruitment, and acute-phase responses. In poultry health, IL-1Ra plays an important role in modulating inflammatory responses during infections such as avian influenza virus, Newcastle disease virus, infectious bronchitis virus, Salmonella spp., and Eimeria (coccidiosis), helping to balance effective pathogen clearance with prevention of excessive tissue damage in respiratory and intestinal tissues. Dysregulation of IL-1/IL-1Ra balance may influence disease severity, growth performance, and flock welfare. As a marker of anti-inflammatory regulation, chicken IL-1Ra is relevant in vaccine evaluation, immune modulation studies, and genetic selection for improved disease resilience. In avian immunology research, characterization of IL-1Ra supports investigations into cytokine network regulation, resolution of inflammation, and comparative innate immune control mechanisms relevant to both poultry production and broader vertebrate inflammatory biology.