Viral infections represent a major global health challenge due to the rapid emergence of new pathogens, increasing antiviral drug resistance and limited efficacy of traditional treatments against evolving viruses. Nanotechnology is a promising interdisciplinary approach to fighting viral diseases, which can perform direct viral inactivation, targeted drug delivery, immune modulation, vaccine development, rapid diagnostics, and prevention of infection. This review offers an in-depth and critical overview of the major antiviral nanoparticle platforms, including metallic, metal oxide, carbon-based, polymeric, lipid-based, and bio-inspired nanoparticles. In this article, we employ a comparative framework to systematically analyze classes of nanoparticles based on their physicochemical properties, molecular mechanisms of antiviral action, biomedical applications, and translational potential. Antiviral mechanisms are discussed within the framework of the viral life cycle, including the inhibition of viral attachment and entry, destruction of viral envelope and capsid integrity, suppression of intracellular viral replication, reactive oxygen species-mediated viral inactivation, immune-modulation, and nanoparticle-assisted therapeutic delivery. Moreover, the review critically discusses the increasing biomedical applications of antiviral nanoparticles in therapeutics, vaccine delivery, diagnostics, antiviral coatings, gene therapy and precision nanomedicine, while highlighting the clinically successful technologies such as lipid nanoparticle-based mRNA vaccines. Special attention is paid to the main obstacles in clinical translation, such as nanotoxicity, biodistribution, manufacturing scalability, regulatory challenges, and the lack of standard evaluation protocols. Finally, major knowledge gaps and future research priorities are highlighted, focusing on the design of multifunctional, clinically translatable and regulatory-compliant nanoplatforms. This review offers insights on antiviral nanomedicines and practical insights for the rational design and successful clinical translation of next-generation antiviral nanoparticle.