The singer has helped fight the stigma of HIV/AIDS through his non-profit, the Elton John AIDS Foundation, since its formation in 1992.
At the event, which took place on World AIDS Day, John told attendees: “There are very few people on this planet who have dedicated themselves to a lifetime of service to save millions of lives like Dr Fauci.”
He added: “His unwavering commitment to public health and innovation has transformed the approach to HIV.
“And it is his leadership and persistence that will ultimately help us overcome the Covid-19 pandemic.”
Dr Fauci, who has served as the director of the National Institute of Allergy and Infectious Diseases since 1984, previously worked as the National Institutes of Health's (NIH) AIDS coordinator.
The 79-year-old also served as the first director of the NIH's Office of AIDS Research from 1988 to 1994.
He faced protests from activists and organisations for his handling of the deadly disease, but later collaborated with activists on research and the development of treatments, according to CNN.
In a video that was streamed at the US Global Leadership Coalition's event on Tuesday, Dr Fauci spoke about the beginning of the epidemic as “one of the darkest periods of (his) life.”
He described having to “put Band-Aids on haemorrhages with no drugs available, watching literally all of my patients die.”
Dr Fauci added: “It's something that just stuck with me, of how that feels when you have people that you want to save that you can't.”
The 79-year-old also helped create the Emergency Plan for AIDS Relief, which was a programme started during George W Bush’s presidency in 2003 that has helped save the lives of millions of people with HIV/AIDS around the world, particularly in Sub-Saharan Africa.
“The impact is extraordinary and it's the gift that keeps giving,” he said on Tuesday evening, in reference to the programme.
“It created a system that you can actually deliver the kind of care, prevention and treatment in a region and in a system that most people blew off as being impossible.”
Dr Fauci added that the fight against HIV/AIDS will continue, but said that he remains optimistic that it will be eradicated while he is still alive.
“When Covid essentially becomes the rearview mirror, HIV is still going to be there, and that's the thing that we have to do,” Dr Fauci said.
He added: “We have to keep our eye on that and never let that -- the end game of ending this is, to me, we're going to get there, and we're going to get there while I'm still around, I can tell you.”