Stevie Wonder told a packed park full of fans that he was scheduled to go under the knife for a kidney transplant.
The legendary musician dropped the bombshell news Saturday night as he was finishing his set across the pond at the British Summer Time Hyde Park music festival.
"I'm going to have surgery, I'm going to have a kidney transplant in September of this year," Wonder said to a stunned audience.
"I'm all good, I'm all good," the singer said, adding that he had already found a donor.
Wonder also thanked the crowd for all the love, but said he wanted to tell people what was going on, as rumors had already began swirling that he was having health issues.
"You don't have to hear no rumors about nothing, I told you what's up ... I'm good," he said.
The crowd was shocked at first, but then erupted into applause and screams of support for Wonder as he revealed his health battle.
The kidney transplant was a bit of sadness in an otherwise rocking evening. Along with his classic hits, Wonder played tributes to artists who have passed away, including songs by** Michael Jackson, Amy Winehouse, Prince** and Aretha Franklin.
He also sang a version of John Lennon's famous track, "Imagine."
Wonder is part of a group of mega stars who are headlining the Hyde Park music festival, including Celine Dion and Barbra Streisand.
Some big stars have been flocking to the festival, including Adele and Margot Robbie, who were both seen attending Friday's show.