From bringing his European Cup winning squad to Omagh in the aftermath of the 1998 bomb to giving his backing to the Milk Cup, Northern Ireland holds a special place in Sir Alex Ferguson's heart.
Sir Alex (71) has family links with Belfast and he revealed in his autobiography that his father Alexander actually played a number of times for Glentoran in the 1930s when he worked in the Harland and Wolff Harland shipyard.
The Govan-born man has retained close ties with Northern Ireland throughout his tenure and yesterday sporting heroes, broadcasting stars and politicians paid tribute to his achievements.
One year after the Omagh bomb which killed 29 people and two unborn twins when it ripped through the Co Tyrone town in 1998, Ferguson brought his team to play to raise funds for those affected. United had just won the European Cup, Premier League and FA Cup. About £200,000 was raised as a result of a series of three matches which also featured Liverpool and Chelsea.
The United boss was described by Milk Cup chairman Victor Leonard as "a great friend of Northern Ireland".
The youth tournament, held annually on the north coast, is world renowned and a host of United stars including David Beckham took part as teenagers.
Former Manchester United players from Northern Ireland also sang his praises, including Keith Gillespie, who played for the Red Devils in the 1990s.
"When I moved full time to England as a 16-year-old he was always there helping you out, because he understood the difficulty in being a young lad and moving away from home," he said.
Ferguson recently tipped Rathcoole man Jonny Evans, a key member of United's defence, to be a future captain of the club.
First Minister Peter Robinson said he had huge respect for Ferguson. "I've met Sir Alex on a number of occasions, most recently on the occasion when he brought a first-rate team to Northern Ireland for the Harry Gregg testimonial," he said.
Deputy First Minister Martin McGuinness also praised the football legend who he said "was hugely supportive of the peace process".
Ulster Unionist sport spokes-man Michael McGimpsey praised Ferguson for ensuring the United scouting network scoured the Northern Ireland for talent "and was second to none in his support for the Milk Cup".
United fan and television personality Eamonn Holmes said Ferguson was irreplaceable.
BBC broadcaster and personal friend of Ferguson Jackie Fullerton said he had never forgotten his working-class roots.
In 2004, Ferguson travelled to Northern Ireland to celebrate the launch of a new Elizabeth Hardie Ferguson Charitable Trust Fund website. Sir Alex is founder and trustee of the fund, which provides financial support for activities that improve the quality of life for children – both their recreational activities and their well being.
The fund was set up in honour of Sir Alex's late mother.
Sporting stars took to social networking sites to pay tribute to Ferguson.
Ferguson led the tributes when the Belfast Telegraph's legendary sports editor Malcolm Brodie passed away in January.
With news of Ferguson's retirement, an Irish League manager has now taken up the mantle of the longest-serving football boss in Europe.
Portadown FC boss Ronnie McFall has been at the helm of the club since 1986 – the same year Fergie took charge at Old Trafford.
Local fans pay tribute to their hero
Samuel Stirling, Ballymena
Most managers build teams, Sir Alex built a club and without what he has done the Premier League would not be the global success story it is today. As much as fans of other clubs may spurn his achievements without him your club would be playing in a small league on the fringes of Europe. 26 years, 38 trophies, one manager. Manchester is red.
Cathy McColgan, Coleraine
I'm devastated by this, he is a legend. I am getting married at Old Trafford next year to my fiance Karl Smith so hopefully Sir Alex will be free to be best man at our wedding!
Noel Rooney, Belfast
There was never an uncertainty when Sir Alex was in charge of Manchester United. Great players came and went but we knew Fergie would get it right. That uncertainty is going to be there now, for the first time in my lifetime.
Lawrence McPeake, Ballymena
Fergie made Manchester United. He was our bus driver steering United into winning trophies in the style United has become accustomed to. A true gent and legend who will go down in folklore and the history of United.
Mervyn McIntyre, Ballymoney
Sir Alex Ferguson's name will be forever in our hearts. He came, he saw and he conquered and made our club the best in the world. It was a marriage made in heaven. Manchester United – where legends are made.
John White, Carryduff Manchester United Supporters Club (pictured left with Alex Ferguson)
For the last 27 years Sir Alex Ferguson has made Manchester United the kings of England, the most revered club in the land – hated by everyone, apart from Manchester United fans. That's why we love him – look at his achievements with us.
Mark Stewart, Ballymena
I am gutted that he has resigned but the memories he has given us are remarkable and what he has achieved will never again be repeated in footballing history. As a director of Manchester United he will still mastermind greatness.
Gary Dornan, Belfast
It's the end of an era. We all will miss the master and I'm privileged to be going to Sunday's game. It will be emotional but looking forward to it. Thanks for everything Sir Alex Ferguson.