Equine CCL5 (C–C motif chemokine ligand 5, also known as RANTES – Regulated upon Activation, Normal T cell Expressed and Secreted) is a proinflammatory chemokine that regulates immune cell recruitment and inflammatory responses in horses (Equus caballus). CCL5 is a member of the CC chemokine family, which also includes CCL3 (MIP-1α), CCL4 (MIP-1β), and CCL2 (MCP-1), chemokines that coordinate leukocyte trafficking during immune activation. In horses, CCL5 is produced primarily by activated T lymphocytes, macrophages, dendritic cells, platelets, and epithelial cells in response to infection, inflammatory stimuli, or tissue injury, and it exerts its biological effects mainly through binding to the chemokine receptors CCR1, CCR3, and CCR5, promoting chemotaxis and activation of T cells, monocytes/macrophages, eosinophils, and natural killer (NK) cells at sites of inflammation. In equine health, CCL5 contributes to immune responses associated with respiratory diseases such as equine asthma (recurrent airway obstruction), viral infections, and inflammatory airway conditions, where chemokine-mediated recruitment of leukocytes to lung tissues is a key component of the inflammatory response. Because horses are commonly studied in respiratory disease, inflammatory disorders, and comparative immunology, equine CCL5 is investigated in research on chemokine-regulated leukocyte trafficking, airway inflammation, and immune responses to infectious and environmental triggers.