Wolbachia, a vertically transmitted intracellular bacterium, induces resistance to RNA viral infections in Drosophila melanogaster. The study shows that Wolbachia infection reduces the viral load of Drosophila C virus (DCV) in infected flies, and also increases resistance to two other RNA viruses, Nora virus and Flock House virus (FHV), but not to a DNA virus, Insect Iridescent Virus 6 (IIV-6). These results indicate that Wolbachia is a significant factor in Drosophila resistance to RNA viruses and suggest that the host's response to pathogens depends on interactions with other microorganisms. This is the first report of a strong beneficial effect of Wolbachia in Drosophila. The induced resistance to natural viral pathogens may explain Wolbachia's prevalence in natural populations and represents a novel Wolbachia-host interaction. The study also shows that Wolbachia is maternally transmitted and that its presence is associated with resistance to DCV. The resistance to DCV is likely due to Wolbachia interfering with virus proliferation. Wolbachia also protects Drosophila from Nora virus and FHV, but not IIV-6. The study highlights the complex interactions between Wolbachia and viral infections and suggests that Wolbachia may influence the host's immune response to viral infections. The findings have implications for understanding the role of Wolbachia in host immunity and for potential applications in controlling viral diseases in insects.Wolbachia, a vertically transmitted intracellular bacterium, induces resistance to RNA viral infections in Drosophila melanogaster. The study shows that Wolbachia infection reduces the viral load of Drosophila C virus (DCV) in infected flies, and also increases resistance to two other RNA viruses, Nora virus and Flock House virus (FHV), but not to a DNA virus, Insect Iridescent Virus 6 (IIV-6). These results indicate that Wolbachia is a significant factor in Drosophila resistance to RNA viruses and suggest that the host's response to pathogens depends on interactions with other microorganisms. This is the first report of a strong beneficial effect of Wolbachia in Drosophila. The induced resistance to natural viral pathogens may explain Wolbachia's prevalence in natural populations and represents a novel Wolbachia-host interaction. The study also shows that Wolbachia is maternally transmitted and that its presence is associated with resistance to DCV. The resistance to DCV is likely due to Wolbachia interfering with virus proliferation. Wolbachia also protects Drosophila from Nora virus and FHV, but not IIV-6. The study highlights the complex interactions between Wolbachia and viral infections and suggests that Wolbachia may influence the host's immune response to viral infections. The findings have implications for understanding the role of Wolbachia in host immunity and for potential applications in controlling viral diseases in insects.