Opendra "Bill" Narayan (November 28, 1936 – December 24, 2007) was an HIV/AIDS researcher at the Johns Hopkins School of Medicine and the University of Kansas Medical Center. A veterinarian, Narayan researched animal models of HIV. His focus on finding a vaccine for retroviral infection had some success against a monkey retrovirus, SIV, and he is best known for engineering a type of HIV that could cause AIDS-like disease in monkeys.