The 33-year-old royal and the 'Rocket Man' musician attended the 22nd International AIDS Conference in Amsterdam, Netherlands, to unveil the Men Star Coalition, which aims to help end the AIDS epidemic by 2030.
Harry - who is the co-founder of the African HIV charity Sentebale - said he was ''honoured'' to speak alongside the 71-year-old pop legend, who has dedicated much of his life to helping target and find a cure for the potentially deadly infection with the launch of the Elton John AIDS Foundation in 1992.
Elton was a close friend of Harry's late mother, Princess Diana - who died in a car accident in Paris in September 1997 - who in 1987 opened the UK's first purpose built HIV/Aids unit.
He said: ''I am honoured to be sharing the stage with someone who has always put people at the centre of his work. For over a quarter of a century he has worked tirelessly to fund research services and communities around the world. Today, he has come to Amsterdam to announce his latest endeavour: a billion dollar global partnership to break the cycle of male transition of HIV - particularly in sub-Saharan Africa.''
Elton, who works alongside the US President's Emergency Plan for AIDS Relief (PEPFAR) with his foundation, commented on their work and how much more work is still needed in Sub Saharan Africa.
He said: ''Since I founded the Elton John AIDS Foundation a quarter of a century ago, an article of faith for us is that no one gets left behind.
''Our LGBT Fund in partnership with PEPFAR is part of that spirit. The LGBT community has suffered discrimination and isolation in many parts of Sub Saharan Africa which have added to HIV vulnerability and left too many people behind in accessing treatment. I am proud of what we have achieved with this Fund and hope its work can continue.''
Harry reaffirmed how important education in young people and new technology is in helping fight AIDS.
He said: ''We succeed when we put people at the heart of our strategies - when we harness the huge potential of people living with HIV to help guide the delivery of services; when we create platforms for young people to shape and direct the services they rely on.'' - The Duke at #AIDS2018 [sic]''
He added: ''New, energetic and innovative solutions are needed more than ever before - and that is exactly what you are about to see from @eltonofficial and the Men Star Coalition partners. [sic]''
Elton also warned how it is the younger males that are at particular risk due to the rise in infections among the ages of 24 and 35, due to not receiving the screening and treatment they require.
He said: ''Young people are the only age group where HIV infections are rising, not falling. We have to do much, much more to bring men, especially younger men more fully into the fold.''
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