Muhammad al-Jifri, head of the Epidemic and Parasitic Diseases Authority, said on Tuesday the kingdom had 6787 AIDS patients, including 1509 Saudi nationals.
Seventy-seven percent of the patients, aged between 15-49, were men, he said.
The Red Sea province of Jiddah has the largest proportion of cases at 41%.
Last year alone, Saudi authorities registered at least 200 new cases, al-Jifri said.
He added 95% of the patients in Saudi Arabia acquired the virus from "forbidden sexual relations".
Sex outside marriage is prohibited by Islam.
Saudi Arabia has harsh penalties for people who commit adultery or fornication, including imprisonment or the death penalty.
Seven million foreigners live in Saudi Arabia, which has a population of about 19 million people.
AIDS, short for acquired immune deficiency syndrome, is spread most often through sexual contact, contaminated needles shared by drug abusers, infected blood, and from pregnant women to their offspring.
Forty million people worldwide have the virus, about 29 million of them in Africa.
UNAIDS estimates there will be 45 million new infections by 2010 if efforts to fight the epidemic are not bolstered.