Ford had been in increasingly frail health in recent years, only making one appearance at training camp last summer and attending games at Ford Field in a wheelchair. He had at least three heart operations.
The cause of his death wasn't reported.
In his absence, it is expected his son, Bill Ford Jr., will take control of the team. He had already been handling most of the day-to-day operations for the past couple of years.
The Lions, however, haven't commented on the future of the team's ownership.
"Today we are mourning the loss of Mr. Ford and reflecting on the impact that he had on the Lions and our community,” read the team’s statement. “Information related to ownership succession will be communicated at the appropriate time."
Controlling shares of the team's stock are held by Ford's wife, Martha, and Ford Jr.
Meanwhile, former Lions players and fellow NFL owners took to Twitter Sunday to mourn the loss of Ford Sr.
Sending my thoughts and prayers to the Ford Family & @DetroitLionsNFL - Mr. Ford was a visionary that will be missed by us all.— Barry Sanders (@BarrySanders) March 9, 2014
Today the city of Detroit lost a great man! RIP Mr. William Clay Ford— Reggie Bush (@ReggieBush) March 9, 2014
Rest in peace, William Clay Ford Sr.— Jim Irsay (@JimIrsay) March 9, 2014