The reports said more education was needed to combat HIV among gay men
HIV rates among gay men in some African countries are 10 times higher than among the general male population, says research in medical journal the Lancet.
The report said prejudice towards gay people was leading to isolation and harassment, which in turn led to risky sexual practices among gay communities.
But the risks are not limited to gay men, as many of the infected also have female sexual partners.
The report called for greater education and resources in the fight against HIV.
The Oxford University researchers found that the prevalence of HIV/Aids among gay men in sub-Saharan African has been "driven by cultural, religious and political unwillingness to accept [gay men] as equal members of society".
Lead researcher Adrian Smith told the BBC there was "profound stigma and social hostility at every level of society concerning either same-sex behaviours amongst men, or homosexuality".
"This has the consequence that this group becomes extremely hard to reach," he said.
Mr Smith said that gay male sex had always been acknowledged as being particularly dangerous in terms of contracting HIV/Aids.
But gay men were also more likely to be involved in other high-risk behaviours, including sex work, having multiple partners and being in contact with intravenous drug use, he said.
George Kanuma, a gay rights activist in Burundi, told the BBC many men "hide their sexual orientation" to get married and have children, but continue to have sex with men.
"Most of them know that you can contract HIV/Aids or any infection when you are making sex with women, but not when you are having sex with another man," he said.
Mr Smith said there was "a desperate need for delivering a basic package of prevention for HIV", including ensuring supplies of condoms.
"There is also a need to sensitise, educate and train those involved in HIV, the interface with men who have sex with men, to educate those involved in care and prevention activities," he said.
The United Nations Aids agency estimates that 33 million people in the world have HIV, of whom two-thirds live in sub-Saharan Africa.