Published Saturday, 28 January 2012
Aerial view of Windsor Park (© UTV)
The game will be hosted at Windsor Park on Tuesday 15 May this year.
A Man United select team, which is expected to include some big names, will play either a Northern Ireland XI or an Irish League select side.
United play their final game of the season against Martin O'Neill's Sunderland on Sunday 13 May before making the trip to Northern Ireland.
The George Best Carryduff Manchester United Supporters Club arranged the fixture by writing to Sir Alex Ferguson.
Gregg has been one of United's best servants over the years.
He played for the club from 1957 to 1966 and was a goalkeeping coach at Old Trafford between 1978 and 1981.
Gregg, who turns 80 this year, was also a hero during the Munich air crash in 1958 and saved lives in the aftermath of the tragic accident.
Gregg also went down as one of the greats while playing for his country; he represented Northern Ireland from 1954 to 1964.
He has already decided which charities he wants the proceeds from the game to go to: the Manchester United Foundation, the Friends of Cancer Centre and the Elizabeth Hardie Ferguson Charitable Trust Fund.
Ticket details for the match have yet to be announced.