Mouse 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 plays a central role in immune cell recruitment, antiviral defense, and inflammatory signaling in mice (Mus musculus). CCL5 is a member of the CC chemokine family, which also includes CCL3 (MIP-1α), CCL4 (MIP-1β), and CCL2 (MCP-1), chemokines that regulate leukocyte trafficking during immune responses. In mice, CCL5 is produced primarily by activated T lymphocytes, macrophages, dendritic cells, platelets, epithelial cells, and endothelial cells in response to infection, inflammatory stimuli, or tissue injury. CCL5 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 murine models, CCL5 plays important roles in host defense against viral, bacterial, and parasitic infections, as well as in chronic inflammatory and autoimmune diseases such as experimental autoimmune encephalomyelitis (a model for multiple sclerosis), asthma models, and inflammatory arthritis. Because mice are the most widely used genetic model organism in immunology, CCL5 has been extensively studied in knockout and transgenic mouse models to understand chemokine-mediated leukocyte trafficking, inflammatory disease mechanisms, and therapeutic targeting of the CCL5–CCR5 pathway relevant to human immune disorders.