1998–99 :Treble Success

The 1998–99 season saw United complete an unprecedented treble sweep of trophies: the league, FA Cup and Champions League. The success coincided with the club becoming the world's richest and most valuable sporting brand worldwide.United were at the centre of a takeover bid from BSkyB in September 1998, which incited supporters. Ferguson refused to be drawn over the controversy of the deal; he nevertheless praised the company for their work in football. The government later referred the deal to the Mergers Commission, which was blocked in April 1999. On the pitch, United made a steady start in all competitions and lost for the final time in the season against Middlesbrough in December 1998, where Ferguson was absent on bereavement leave. Their route to the 1999 FA Cup Final, which they won 2–0 against Newcastle United, mostly involved ties against fellow league clubs. In the semi-final replay against cup holders Arsenal, Keane was sent off and United conceded a penalty late into the match; but Dennis Bergkamp's effort was saved by Schmeichel. Giggs in extra time ran the length of the pitch and scored what The Times reporter Oliver Holt described as "a goal of breathtaking skill". In the league, United regained the title after a closely fought challenge from Arsenal.

After finishing second in their Champions League group – behind Bayern Munich and ahead of Barcelona – and knocking-out Inter Milan in the quarter-final stage, United faced Juventus in the last four. An injury time goal scored by Giggs in the first leg earned the team a 1–1 draw, but in spite of conceding an away goal, Ferguson was adamant of United's chances of reaching the final: "...something tells me we are going to win. The nature of our club is that we torture ourselves so much that the only way to get relief is by winning over there. It will be a great game and hopefully I am right."At the Stadio delle Alpi, striker Filippo Inzaghi scored twice to put Juventus 3–1 up on aggregate. Keane headed in a Beckham cross to halve the deficit, but was later shown a yellow card for a foul on Edgar Davids, which prevented him from playing in the final. Yorke equalised, before Cole added a third to win the match outright. Ferguson described his captain's performance as "the most emphatic display of selflessness ... he inspired all around him. I felt it was an honour to be associated with such a player". In Barcelona, where the 1999 UEFA Champions League Final was staged against Bayern Munich, United conceded inside six minutes, through Mario Basler's free kick. Sheringham equalised from a corner late into the match and Solskjær in added time scored the winner, from another set piece. When interviewed moments after the match, Ferguson said:

(I can't believe it. I can't believe it. Football, bloody hell. But they never gave in and that's what won it.)

Ferguson and Schmeichel, the stand-in captain, jointly lifted the cup during the trophy presentation. A crowd of over 500,000 people turned out on the streets of Manchester to greet the players, who paraded through the city in an open-top bus. As European champions, United were invited to play in the Intercontinental Cup. The club also entered the inauguralClub World Championship, which was held in Brazil. Given the possibility of a hectic fixture schedule, United withdrew from the FA Cup, becoming the first holders to do so. In later years, Ferguson cited the decision had to do with England's failed 2006 FIFA World Cup bid, and he expressed regret in how the club dealt with the situation.