FIFA president Sepp Blatter hailed Sir Alex Ferguson as one of football's "greats" after the Manchester United manager announced he would retire at the end of the season.
Ferguson has had a career the likes of which will never be seen again. He won his 49th trophy in United's 20th league championship.
Blatter, who gave Ferguson with a lifetime achievement award last year, said on Twitter: "Just heard Sir Alex Ferguson is retiring at end of season. His achievements in the game place him without doubt as one of the 'greats'."
UEFA president Michel Platini hailed Ferguson as "a true visionary", and added: "Sir Alex has made a massive contribution to football, not only in Scotland and in England, but across Europe and beyond.
"His dedication, his attention to detail and his unique eye for talent, as both the manager of Manchester United FC and Aberdeen FC, has brought rich rewards over a 30-year period. His CV is almost unique in a results-based profession that normally focuses on short-term solutions rather than long-term vision.
"He is a true visionary and I hope that, having helped us in the past through various coaching initiatives, he will continue to collaborate with UEFA to share his fantastic knowledge with the next generation of up-and-coming European coaches who all wish to emulate his achievements in the sport."
Premier League chief executive Richard Scudamore said Ferguson's "drive, ambition, skill, passion and vision" have forever altered the landscape of football, and he said: "The Premier League has had the privilege to witness many great players, managers and teams. No one has made as great a contribution to the Premier League than Sir Alex Ferguson.
"His drive, ambition, skill, passion and vision have not only shaped Manchester United, but in many ways the game of football as we now know it. Sir Alex and his teams during the Premier League era have set the pace others have had to follow; 13 titles out of 21 seasons is a phenomenal achievement."
Professional Footballers' Association (PFA) chief executive Gordon Taylor told Press Association Sport: "The game of football will be a lot poorer place without him. He has been quite simply the best.
"He followed in Sir Matt Busby's footsteps and even surpassed him. He will be also be the toughest act to follow."