The little girl, now two-and-a-half, was born with the virus but has been off treatment for around a year with no signs of infection.
If the American youngster, from Mississippi, stays healthy, it would be one of the first reported cures of HIV.
She was given faster and stronger treatment than is usual, with doctors giving her drugs within 30 hours of being born.
Dr Hannah Gay, in charge of the youngster's treatment, said: "I just check for the virus and keep praying that it stays gone."
More tests are set to take place to see if the treatment could be used on other kids.
Specialists say Sunday’s announcement, at a major AIDS meeting in Atlanta, offers promising clues for efforts to eliminate HIV infection in children, especially in AIDS-plagued African countries where too many babies are born with the virus.
Virus expert Dr Deborah Persaud, said: "This is proof of concept that HIV can be potentially curable in infants."