Viruses constitute the most abundant biological entities on Earth, yet they remain markedly underrepresented in astrobiological research frameworks. This mini-review examines three interrelated dimensions of their relevance: their potential roles in the origin and early evolution of life, the constraints on their existence independent of complex ecosystems, and the challenges and opportunities they present for extraterrestrial life detection. Competing hypotheses - including viruses-first, viroids-first, and models situating viral emergence during the transition from the First Universal Common Ancestor to the Last Universal Common Ancestor - highlight viruses and virus-like entities as candidate participants in precellular evolution and as powerful drivers of subsequent cellular diversification. Although obligately dependent on host cellular machinery for replication, viruses display exceptional resilience in extreme terrestrial environments and under simulated interstellar conditions, suggesting that virions may persist where cellular life cannot. Detection of extraterrestrial viruses is currently hindered by the absence of validated biosignatures, instrument biases favoring cellular definitions of life, and limitations in metagenomic identification tools. Future missions targeting Mars or the subsurface oceans of icy moons offer unique opportunities to test viral origin hypotheses and to incorporate virus-aware detection strategies. Integrating virology into astrobiological thinking is therefore essential for a more complete understanding of life’s possible distribution and evolutionary trajectories beyond Earth.
