The Detroit area native's death is under investigation and police have said they did not immediately know the cause.
No details regarding the circumstances of Kelly's death Tuesday were immediately released.
"Mike was an irresistible force in contemporary art," Kelley Studio said in a statement Wednesday. "We cannot believe he is gone. But we know his legacy will continue to touch and challenge anyone who crosses its path. We will miss him. We will keep him with us."
Paul Schimmel, chief curator of the Museum of Contemporary Art, told the Times he is "devastated" by the news.
"Mike is our great Los Angeles artist," Schimmel said. "He's the one that changed the game for a whole generation. If one could point the finger singularly, he's it. As an artist, a curator, as a kind of passionate advocate for this community and his generation, he's a real giant."