The MC - real name Keith Elam - is understood to have passed away on April 19.
In a statement, Guru's partner Solar told AllHipHop: "The world has lost one of the best MCs and hip-hop icons of all-time - my loyal best friend, partner and brother Guru."
In March, Guru underwent surgery after suffering a heart attack. He was recently reported to have been in better health and heading towards recovery.
However, Solar revealed that Guru had also been battling cancer for over a year, saying: "This is a matter that Guru wanted private until he could beat it, but tragically, this did not happen. The cancer took him. Now the world has lost a great man and a true genius."
Formed in 1985, Gang Starr, which also features DJ Premier, are most known for their inimitable combination of New York swing jazz and hip-hop. Their hits include 'Ex-Girl To The Next Girl' and 'Positivity'.