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.
"I can't stop crying over the sad news. I have always admired Michael Jackson. The world has lost one of the greats, but his music will live on forever! My heart goes out to his three children and other members of his family. God bless," via her publicist.
"I was so excited to see his show in London. We were going to be on tour in Europe at the same time and I was going to fly in to see him. He has been an inspiration throughout my entire life and I'm devastated he's gone!," via her publicist.
"A friend of Michael's for the last 35 years, I call on people around the world to pray for him and his family in the hour. I have known Michael since we were both teens, worked with him, marched for him, hosted him at our House of Justice headquarters in New York, and we joined together to eulogize our mutual idol, James Brown. I have known him at his high moments and his low moments and I know he would want us to pray for his family," via his publicist.
"Words cannot begin to express my heartfelt sorrow upon hearing the news of Michael Jackson's passing. I was blessed to be able to work with, and witness firsthand, his tremendous talent and growth through the years as he truly became an icon.
Today we have all lost a legend who has touched each of our lives through his music and showmanship over the past five decades.
To his family, the entire Jackson clan, and to all his adoring legions of fans throughout the world, my prayers and deepest condolences to all."
"We have lost an icon in our industry and my heartfelt condolences go out to his family and children in this hour of sorrow that they are now going through. He will live on in my memory and most definitely through the music he shared with so many," via her publicist.
"I knew Michael as a child and watched him grow over the years. Of all the thousands of entertainers I have worked with, Michael was THE most outstanding. Many have tried and will try to copy him, but his talent will never be matched," via his publicist.
"Music has lost a king, music has lost an icon, music has lost a friend. It's unbelievable, but we don't have any choice but to believe it," via The Los Angeles Times.
"Words can't begin to describe my sadness for the loss of Michael Jackson. I was honored and humbled to have the opportunity to perform with him several times and he had a profound influence on my career. Michael forever changed the world of music and entertainment and I will always remember him for his kind and sweet spirit," via his publicist.
"Michael Jackson was my inspiration. Love and blessings," via Twitter.
"Dazed in the studio. A major strand of our cultural DNA has left us. RIP MJ. I think we'll mourn his loss as well as the loss of ourselves as children listening to Thriller on the record player," via Twitter.
"NO OMG ... sending my love and prayers out to Michael and his family ... I feel sick," via Twitter.
"If it were not for Michael Jackson I would not be where or who I am today. His Music and Legacy will live on Forever. Prayers to the fam. R.I.P.," via Twitter.
"Death comes to all. But great achievements build a monument." He IS and WAS the greatest entertainer of all times...Peace to you brother," via Twitter.
"I have no words.. I loved Michael Jackson.. RIP..," via Twitter.
"Michael Jackson has passed away. His spirit and creative influence will live on through his music that we have loved for decades," via Twitter.