Below, a roundup of what some of Jackson's famous fans and friends are saying.
"I am so very sad and confused with every emotion possible. I am heartbroken for his children, who I know were everything to him, and for his family. This is such a massive loss on so many levels, words fail me," via her publicist.
"My heart ... my mind ... are broken. I loved Michael with all my soul and I can't imagine life without him. We had so much in common and we had such loving fun together. ... My life feels so empty. I don't think anyone knew how much we loved each other. The purest most giving love I've ever known. Oh God! I'm going to miss him. I can't yet imagine life with out him. But I guess with God's help ... I'll learn. I keep looking at the photo he gave me of himself, which says, 'To my true love Elizabeth, I love you forever.' And, I will love HIM forever," via her publicist.
"One of the greatest moments of my entire life was being on stage with Michael Jackson. This has been a devastating day in music history ... it's been very painful to even compose myself now. I'm holding back the tears," via an interview with "Good Morning America."
"What a great time. What a great entertainer. There will never be anybody [like him] ... So our condolences go out to his family and let's take time ... to do the right thing and honor the beauty of what Michael Jackson was and not the craziness and all of the circus things that the media can grab a hold to sometimes and just go nuts. Let's just honor that guy for all he's done and that's all you can say," via an interview with "Extra."
"I am absolutely devastated at this tragic and unexpected news. For Michael to be taken away from us so suddenly at such a young age, I just don't have the words. Divinity brought our souls together on 'The Wiz' and allowed us to do what we were able to throughout the '80s. To this day, the music we created together on 'Off The Wall,' 'Thriller' and 'Bad' is played in every corner of the world and the reason for that is because he had it all ... talent, grace, professionalism and dedication. He was the consummate entertainer and his contributions and legacy will be felt upon the world forever. I've lost my little brother today, and part of my soul has gone with him," via his publicist.
"My heart is overcome with sadness for the devastating loss of my true friend Michael. He was an extraordinary friend, artist and contributor to the world. I join his family and his fans in celebrating his incredible life and mourning his untimely passing," via her publicist.
"We have lost a genius and a true ambassador of not only Pop music but of all music. He has been an inspiration to multiple generations, and I will always cherish the moments I shared with him on stage and all of the things I learned about music from him and the time we spent together. My heart goes out to his family and loved ones," via his Web site.