Chicken Macrophage Colony-Stimulating Factor (M-CSF) is a cytokine that regulates the development, proliferation, and survival of monocytes and macrophages in chickens (Gallus gallus). M-CSF is produced by several cell types, including fibroblasts, epithelial cells, and stromal cells, in response to tissue signals and inflammatory stimuli. Chicken M-CSF binds to the colony-stimulating factor-1 receptor (CSF1R), a receptor tyrosine kinase expressed on monocytes and macrophage lineage cells, activating intracellular signaling pathways such as PI3K–AKT, ERK/MAPK, and JAK–STAT that promote differentiation and maintenance of macrophage populations. Through these mechanisms, M-CSF supports macrophage-mediated immune surveillance, phagocytosis, tissue homeostasis, and inflammatory responses. Because macrophages play a key role in host defense, M-CSF–mediated macrophage function is important for maintaining immune health and resistance to infection in poultry. In cell culture, recombinant chicken M-CSF is commonly used to promote differentiation of chicken monocytes into macrophages and to support macrophage proliferation and functional assays in vitro. Chicken M-CSF is also studied in avian immunology and animal model research, including investigations of macrophage responses to important poultry pathogens such as avian influenza virus, Salmonella spp., and Eimeria species.