The exact origin of HIV is unknown, but it is suspected to have come from Africa.

Studies suggest that chimpanzees, native to West Africa, were the origin of HIV. Experts feel that chimpanzees have harbored a similar virus, called SIVcpz for a few hundred thousand years. Unlike humans, infected animals do not develop AIDS from this virus. Transmission of the virus from the animal to the human population may have been through a contaminated bites or scratches, or from eating these animals. At some point, the virus changed, or mutated, into HIV.

The oldest case of HIV infection has been authenticated from a blood sample collected in 1959 from an African man.