According to the BBC, Jarez Posey's manager told US media that the artist was found unconscious on the bathroom floor of a friend's home in Los Angeles.
Coolio began making music in the 1980s, but cemented his place in hip-hop history when he recorded Gangsta's Paradise in 1995.
The exact causes of his death are not yet known.
However, Mr Posey told TMZ, which first reported the news, that medics believed he might have gone into cardiac arrest.
Coolio, whose real name is Artis Leon Ivey Jr., won a Grammy for Gangsta's Paradise, which was part of the soundtrack to the film Dangerous Minds starring Michelle Pfeiffer.
The haunting track continues to be widely heard and has just passed one billion streams on Spotify, according to its official website.
Active in Music to the End: Coolio's Music Career
With a career that covers four decades, Coolio recorded a total of eight albums and won an American Music Award and three MTV Video Music Awards.
His other successes were Fantastic Voyage, Rollin' With My Homies, 1, 2, 3, 4 (Sumpin' New) and Too Hot.
He was active right up until his death – Coolio was in the middle of a tour with other '90s stars like Vanilla Ice and Young MC, and they played a concert in Texas just a few days ago.
"Freaked out just to hear my good friend Coolio passed away," Vanilla Ice tweeted.
"Freaked out just to hear my good friend Coolio passed away," Vanilla Ice tweeted.
"This is sad news. I've seen firsthand this man's rise to the top of the industry," said fellow rapper and actor Ice Cube.