Sir Alex and Lady Cathy were married for 57 years, with the couple producing three children.
They first met in 1964 when both were working at a typewriter factory and got married two years later.
Sir Alex would go on to manage Manchester United for 27 years, becoming the most successful manager in British football history.
A statement released by the Ferguson family on Friday afternoon read: "We are deeply saddened to confirm the passing yesterday [Thursday] of Lady Cathy Ferguson, survived by her husband, three sons, two sisters, 12 grandchildren and one great-grandchild."
"The family asks for privacy at this time."
Man Utd issued a statement on Friday which read: "Everyone at Manchester United sends our heartfelt condolences to Sir Alex Ferguson and his family on the passing of Lady Cathy, a beloved wife, mother, sister, grandmother and great-grandmother, and a tower of strength for Sir Alex throughout his career."
Lady Cathy famously talked Sir Alex out of an early retirement in 2002, and he would go on to manage the Red Devils for another 12 years.
When he finally announced his retirement in 2013, Sir Alex said: "My wife Cathy has been the key figure throughout my career, providing a bedrock of both stability and encouragement. Words are not enough to express what this has meant to me."
