Equine CXCL9 (C-X-C motif chemokine ligand 9), also known as MIG (monokine induced by interferon-γ), is a proinflammatory chemokine belonging to the CXC chemokine family, which also includes CXCL10 (IP-10) and CXCL11 (I-TAC) that regulate T-cell recruitment during interferon-driven immune responses. In horses (Equus caballus), CXCL9 is produced by macrophages, dendritic cells, endothelial cells, and epithelial cells in response to interferon-γ (IFN-γ) and inflammatory stimuli during infection or immune activation. CXCL9 signals primarily through the chemokine receptor CXCR3, which is expressed on activated T lymphocytes, natural killer (NK) cells, and other immune cells, promoting chemotaxis and accumulation of these cells at sites of infection or inflammation. In equine health, CXCL9 contributes to cell-mediated immune responses against intracellular pathogens, particularly in tissues such as the respiratory tract and lymphoid organs. CXCL9-mediated recruitment of Th1-type T cells is important in immune responses to viral and bacterial infections, including diseases such as equine herpesvirus infections, where interferon-driven chemokine signaling helps coordinate antiviral immunity and inflammatory responses. Consequently, equine CXCL9 is studied in veterinary immunology and infectious disease research to better understand T-cell trafficking, interferon-mediated immunity, and host–pathogen interactions in horses.