Joel Glazer, joint chairman of the Manchester United board with brother Avie, pinpointed the 2008 Champions League final penalty shootout success over Chelsea as a highlight among the many memories of Ferguson's time at the club.
He said: "Alex has proven time and time again what a fantastic manager he is but he's also a wonderful person.
"His determination to succeed and dedication to the club have been truly remarkable. I will always cherish the wonderful memories he has given us, like that magical night in Moscow."
Avie Glazer added: "I am delighted to announce that Alex has agreed to stay with the club as a director.
"His contributions to Manchester United over the last 26 years have been extraordinary and, like all United fans, I want him to be a part of its future."