Chicken G-CSF (Granulocyte Colony-Stimulating Factor, CSF3) is a hematopoietic cytokine belonging to the colony-stimulating factor family, which also includes GM-CSF (CSF2) and M-CSF (CSF1) that regulate the development and function of myeloid immune cells. In chickens (Gallus gallus), G-CSF is produced by macrophages, endothelial cells, fibroblasts, and other stromal cells in response to infection, inflammatory cytokines, or tissue injury. Chicken G-CSF binds to the G-CSF receptor (CSF3R) expressed on myeloid progenitor cells in hematopoietic tissues, activating intracellular signaling pathways such as JAK/STAT, MAPK/ERK, and PI3K–AKT, which promote the proliferation, differentiation, and survival of granulocytic precursor cells, particularly heterophils, the avian functional equivalent of mammalian neutrophils. In poultry immunity, G-CSF plays an important role in innate immune defense by regulating heterophil production and mobilization during bacterial infection or inflammatory responses. Chickens are also widely used as animal models for studying host–pathogen interactions and innate immune responses to bacterial infections, and G-CSF–mediated heterophil responses have been examined in chicken models of Salmonella enterica infection, where increased granulocyte production and recruitment help control intestinal colonization and systemic spread of the pathogen, providing insights relevant to both poultry disease control and food safety research.