The innate immune system serves as the body’s primary defence against all pathogen infections, including viruses. It rapidly detects and responds to viral components, enabling an effective reaction at each stage of the viral replication cycle. This chapter explores how the innate immune system utilises pattern recognition receptors, such as Toll-like receptors and RIG-I-like receptors, to identify viral structures like capsid proteins and viral nucleic acids. The activation of these receptors triggers the release of type I interferons, particularly IFN-α and IFN-β, as well as other cytokines and chemokines. These molecules are crucial in inhibiting viral replication and inducing an antiviral state in neighbouring cells. Furthermore, the cytokines and chemokines facilitate the recruitment of key innate immune cells such as macrophages, dendritic cells, and natural killer cells, which enhance the overall immune response and directly eliminate infected cells. This chapter provides a comprehensive understanding of the complex interplay between viral pathogens and the host immune system. It also examines the antiviral role of the complement system and the transition from innate to adaptive immunity, a shift often necessitated by prolonged viral replication or sophisticated immune evasion strategies employed by viruses. By detailing these interactions and emphasising the crucial roles of interferons and immune evasion strategies, this chapter highlights the importance of early innate immune responses in controlling infections.