Glazer gained a global profile through his ownership of United, one of the biggest and best supported football clubs in the world.
But he was deeply unpopular with hardcore United fans after loading the club with hundreds of millions of dollars in debt following a 2005 buyout.
His death was announced on the website of the Tampa Bay Buccaneers American football team, one of his other sports franchises.
"The Tampa Bay Buccaneers are saddened to announce the passing of Owner/President Malcolm Glazer earlier this morning at the age of 85," the statement said.
"A dynamic business leader, Glazer helped mold the Buccaneers into a model franchise and one respected league-wide."
Under Glazer's stewardship of the Buccaneers, the NFL team enjoyed its first Super Bowl success in 2002.
Shares of Manchester United slipped sharply after Glazer's death was announced on the New York Stock Exchange late Wednesday.
Glazer's death is not expected to have any bearing on the ownership of the club, with his family retaining a 90 percent holding in United.
His sons Joel and Avram Glazer continue to serve as co-chairmen of the club. Another son, Bryan, remains on the United board.
"The thoughts of everyone at Manchester United are with his family tonight," the Premier League club said Wednesday.
Glazer's 2005 takeover of United in a leveraged $1.2 billion buyout triggered widespread protests amongst the club's fans.
Although Glazer's reign coincided with a glut of silverware -- including five Premier League crowns and the 2008 Champions League title -- he remained a hate figure for many supporters.
Fans have complained that Glazer's ownership model has forced United to spend millions of pounds servicing the club's debt -- money which could have been spent in strengthening United's playing staff.
Nevertheless, Glazer found a consistent and vocal ally in Manchester United's legendary former manager Sir Alex Ferguson, who insisted the American had been "great" for the club.
"I am comfortable with the Glazer situation. They have been great," Ferguson said in 2012, a year before he announced his retirement.
"They have always backed me whenever I have asked them. I have never faced any opposition."
COMMENTS (1)
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ
RIP Mr. Glazer. Condolences to the Glazer and United families.