Doctors studied nearly a thousand gay male couples in which one partner was HIV positive, and the other was negative.
Over 8 years, just 15 of the negative men were infected, but all were infected by different partners.
An earlier study proved the same thing among heterosexual couples.
Researchers say the study proves that using antiretroviral therapy to suppress the AIDS virus to undetectable levels also means it cannot be passed on via sex.
"Our findings provide conclusive evidence for gay men that the risk of HIV transmission with suppressive ART is zero," said Alison Rodger, a professor at University College London who co-led the research.
She said this "powerful message" could help end the HIV pandemic by preventing the virus' transmission in high-risk populations.
In this study alone, for example, the researchers estimate that the treatment prevented around 472 HIV transmissions during the eight years.