Click through the gallery to see star tributes to the late athlete.
1 of 11
"You will always be my hero… #MuhammadAli."
2 of 11
"This was one of the strongest and sweetest men I ever met. He elevated the sport of boxing and there will never be another!"
3 of 11
Michael J. Fox
"Ali, the G-O-A-T. A giant, an inspiration, a man of peace, a warrior for the cure. Thank you."
4 of 11
"The greatest there will ever be… The biggest and the best… Rest in peace."
5 of 11
"What is going on?! We are losing all of our national treasures. Our pillars of humanity. He was the greatest!"
6 of 11
"Thank you for always showing me and my family love. He was so kind to everyone he met… We miss you. We love you. You have changed the world. And taught us all something. Rest in peace, Great One."
7 of 11
"Ali! Ali! Ali! #RIP. He told me, 'Hey Knight Rider, you're pretty, but not as pretty as me.' The Greatest's spirit will always be in my heart!"
8 of 11
"Dear Muhammad Ali. I loved that man. He was great from the first day we met him in Miami, and on the numerous occasions when I ran into him over the years. Besides being the greatest boxer, he was a beautiful, gentle man with a great sense of humor who would often pull a pack of cards out of his pocket, no matter how posh the occasion, and do a card trick for you. The world has lost a truly great man. Love, Paul."
9 of 11
"The world has lost a legend and real champion. #RIPMuhammadAli."
10 of 11
"Muhammad Ali is dead at 74! A truly great champion and a wonderful guy. He will be missed by all!"
11 of 11
"Lying here at Caesars after my show tonight in Vegas thinking about the #GOAT, #MuhammadAli, and thinking about how he inspired me and so many to want to be their greatest! #RIP #ALI #Inspiration #SuchALegend."