Cynomolgus Monkey (Macaca fascicularis) Interferon-Alpha (IFN-α) is a type I interferon produced primarily by plasmacytoid dendritic cells and virus-infected cells, where it plays a pivotal role in early innate antiviral immunity. Structurally and functionally highly homologous to human IFN-α, cynomolgus IFN-α signals through the type I interferon receptor complex (IFNAR1/IFNAR2), activating JAK/STAT pathways and inducing interferon-stimulated genes (ISGs) that inhibit viral replication, enhance antigen presentation, and promote natural killer (NK) cell and adaptive immune activation. IFN-α responses are critical in nonhuman primate models of viral infections such as dengue virus, influenza, SARS-CoV-2, Zika virus, simian immunodeficiency virus (SIV), and other emerging pathogens, where interferon dynamics influence viral control, inflammation, and disease severity. Because cynomolgus monkeys are widely used in preclinical vaccine development, antiviral drug testing, and immunotoxicology studies, characterization of IFN-α is essential for evaluating innate immune activation, cytokine profiles, and safety of biologics targeting immune pathways. As both a biomarker and functional mediator of antiviral defense, cynomolgus IFN-α plays a central role in translational research bridging nonhuman primate models and human infectious, autoimmune, and inflammatory diseases.