Details of death: Died from an apparent overdose at his home in Studio City, California.
The former boyfriend of Ariana Grande, he was found at his home in the San Fernando Valley outside Los Angeles at around midday on Friday.
Post Malone said Miller "changed so many lives", while Chance The Rapper said he was "one of the sweetest guys I ever knew".
Miller's death comes several months after he ended a high-profile, two-year relationship with pop superstar Grande, who was often seen as the inspiration for his songs.
This is a developing story.
Miller's family in a statement confirmed the death and called him "a bright light in this world for his family, friends and fans".
According to reports, Miller had still been feeling the emotional impact of his breakup from longtime girlfriend Ariana Grande, as well as her subsequent whirlwind engagement to "SNL" star Pete Davidson shortly after they split.
Miller, whose real name is Malcolm McCormick, had faced a continued battle with drug addiction.
Following new of his death, Miller's famous friends and contemporaries took to Twitter to share their shock and sadness at his passing. Just last month, the Los Angeles Attorney's Office officially charged the rapper with a DUI stemming from a auto accident in May in the San Fernando Valley. "Let's please stop doing that".
While a lot of healing is taking place on the album, Miller had seemingly come to the conclusion that being clear enough to experience your feelings was far superior to just being happy all the time. It's wanting the very best for that person even if at the moment, it isn't you. Grande had every right - as well as a responsibility to herself - to make sure she was looking after herself.
Paste has reached out to a representative for Miller for more information.
The couple had dated for almost two years before Grande broke it off in May. She also responded to a fan who blamed her for the incident which occurred just weeks after their split, revealing that Miller's struggle with sobriety was "toxic" for their relationship.