Cynomolgus Monkey (Macaca fascicularis) Interferon-Beta (IFN-β) is a type I interferon produced by virus-infected epithelial cells, fibroblasts, macrophages, and dendritic cells, where it serves as a critical early mediator of innate antiviral immunity. Highly homologous to human IFN-β, cynomolgus IFN-β signals through the type I interferon receptor complex (IFNAR1/IFNAR2), activating JAK/STAT pathways and inducing interferon-stimulated genes (ISGs) that suppress viral replication, enhance antigen presentation, and promote natural killer (NK) cell and adaptive immune activation. IFN-β responses are central to nonhuman primate models of viral infections including dengue virus, influenza, SARS-CoV-2, Zika virus, and other emerging pathogens, where the timing and magnitude of interferon induction influence viral control, inflammation, and disease severity. Because cynomolgus monkeys are widely used in preclinical vaccine development, antiviral therapeutic testing, and immunotoxicology studies, characterization of IFN-β is essential for evaluating innate immune activation, cytokine dynamics, and safety of biologics targeting immune pathways. As both a biomarker and functional regulator of host–virus interactions, cynomolgus IFN-β plays a pivotal role in translational research bridging nonhuman primate disease models and human infectious, inflammatory, and immune-mediated conditions.