Zebrafish Interferon-γ (IFN-γ) is a type II interferon cytokine that plays an important role in cell-mediated immunity and regulation of antimicrobial and inflammatory responses in zebrafish (Danio rerio). IFN-γ is produced primarily by activated T lymphocytes and natural killer (NK)-like cells following stimulation by intracellular pathogens or immune signaling molecules such as IL-12 and IL-18. Zebrafish IFN-γ binds to interferon-γ receptors expressed on various immune and non-immune cells, activating intracellular signaling through the JAK–STAT pathway, particularly STAT1, which induces expression of interferon-stimulated genes involved in antigen presentation, macrophage activation, and antimicrobial defense. In zebrafish, IFN-γ contributes to activation of macrophages, enhancement of antigen presentation pathways, and control of intracellular pathogens including bacteria and parasites. Zebrafish IFN-γ is widely studied in aquatic immunology and vertebrate disease models; for example, zebrafish models of Mycobacterium marinum infection use IFN-γ expression as a key marker of host immune responses during granuloma formation and mycobacterial pathogenesis.