Human Interferon-Beta (IFN-β) is a type I interferon produced primarily by virus-infected epithelial cells, fibroblasts, macrophages, and dendritic cells, where it functions as a critical early mediator of innate antiviral immunity. Upon recognition of viral RNA or DNA by pattern recognition receptors such as RIG-I, MDA5, and the cGAS-STING pathway, IFN-β is rapidly induced and signals through the type I interferon receptor complex (IFNAR1/IFNAR2), activating JAK/STAT pathways and driving expression of interferon-stimulated genes (ISGs) that inhibit viral replication, enhance antigen presentation, promote natural killer (NK) cell cytotoxicity, and shape adaptive immune responses. IFN-β plays a central role in defense against viral infections including influenza, hepatitis viruses, herpesviruses, SARS-CoV-2, and other emerging pathogens, with impaired or delayed IFN-β responses associated with severe disease outcomes. Conversely, chronic or dysregulated IFN-β signaling contributes to autoimmune and inflammatory conditions such as systemic lupus erythematosus and type I interferonopathies. Clinically, recombinant IFN-β is an established therapy for relapsing-remitting multiple sclerosis due to its immunomodulatory properties. As both a biomarker and therapeutic agent, human IFN-β is central to research on antiviral defense, immune dysregulation, neuroinflammation, and development of interferon-based or interferon-modulating treatments.