Highlight: The present report reveals for the first time natural lentiviral infection of wild Indian NHPs, rhesus monkeys (Macaca mulatta) and langurs (Semnopithecus entellus) by SIVs that are phylogenetically diverse from all known SIVs, including “SIVmac”, which infects captive rhesus monkeys. The novel SIVs are intriguingly homologous to HIV-1, based on serology and partial lentiviral genomic sequence analyses. Diverse lenti-viruses infect human and nonhuman primates (NHPs). There are more than 45 different “species-specific” simian immunodeficiency viruses (SIVs) that infect their cognate NHP hosts in natural habitats in Africa. Indian NHPs are not known to be infected by SIVs in the wild. Conventionally SIVs are named after their natural hosts, except for SIVmac, which infects captive rather than wild rhesus macaques. SIVmac is therefore a misnomer. It is a genetic variant of the African SIVsmm, which infects wild African sooty mangabey monkeys. SIVsmm is the progenitor of human immunodeficiency virus (HIV-2), while SIVcpz that infects wild chimpanzees is the progenitor of HIV-1. Although natural infections cannot be easily studied in wild NHP populations, we have previously reported co-infection of wild Indian NHPs by other retroviruses: simian retroviruses (SRVs) and Simian Foamy viruses (SFV). Apart from zoonosis, transmission of pathogens from humans to animals: anthroponosis, has also been reported in literature.