Chicken CX3CL1 (C-X3-C motif chemokine ligand 1), also known as fractalkine, is a chemokine belonging to the CX3C chemokine family, characterized by three amino acids separating the first two conserved cysteine residues. CX3CL1 is unique among chemokines because it exists in both a membrane-bound form and a soluble form, allowing it to function in leukocyte adhesion as well as chemotaxis. In chickens (Gallus gallus), CX3CL1 is produced primarily by endothelial cells, epithelial cells, macrophages, and other activated tissue cells in response to infection, inflammatory cytokines, or tissue damage. CX3CL1 binds to its receptor CX3CR1, which is expressed on monocytes/macrophages, natural killer (NK)-like cells, and subsets of T lymphocytes, promoting recruitment, adhesion, and activation of these immune cells at sites of inflammation. In avian immunity, CX3CL1 contributes to host defense during viral and bacterial infections, including important poultry diseases such as avian influenza, Newcastle disease virus, and bacterial respiratory infections, where chemokine-mediated immune cell trafficking is essential for pathogen control. Because leukocyte recruitment and inflammatory signaling are key components of avian immune responses, chicken CX3CL1 is studied in avian immunology, host–pathogen interaction research, and vaccine development to better understand mechanisms regulating immune cell migration and inflammatory responses in poultry.