Elton John says he's devastated by the death of his "beloved friend" George Michael -- saying, "I am in deep shock."
Elton -- who famously collaborated with George for the 1992 hit, "Don't Let the Sun Go Down on Me" -- posted a tribute to his longtime friend on Instagram.
"I am in deep shock. I have lost a beloved friend - the kindest, most generous soul and a brilliant artist. My heart goes out to his family and all of his fans. @GeorgeMichael #RIP."
Michael died Sunday at his home in England. He was 53.