The 31-year-old signed a four-year deal at the Stadium of Light after the clubs agreed an undisclosed fee, understood to be in the region of ?1million.
The move brings to an end Brown's 15-year stay at Old Trafford and Ferguson was full of praise for the England international.
Fresh start: Brown has joined Sunderland
He said: 'Wes has been a great asset to the club during the most successful period in its history.
'He was a product of the youth systemand marked himself out from an early age as one of his generation's most natural defenders. In his time with us, he certainly became a favourite with the fans for his no-nonsense approach to the game and hisinfectious personality.
'It's always the hardest of decisionsto let loyal servants go. But life moves on and, unquestionably, Wes will get the chance to make a real contribution to Steve Bruce's Sunderland, and I'm delighted to be passing him into such good hands.
'Everyone connected with United wishes him a long and happy stay at Sunderland.'
Sunderland manager Bruce said: 'We are delighted to welcome a player of Wes' ability, experience and character to the club. Hehas been a fantastic professional for Manchester United through the years and not only will he strengthen our defensive options, he will also bring with him a winning mentality and level of maturity which can only be positive for the players around him.'
Next up? John O'Shea (left) has also been targeted by Sunderland manager Steve Bruce
Fellow defender John O'Shea, 30, is also expected to agree terms having undergone a medical on Thursday morning, while Darron Gibson is firmly in Steve Bruce's sights as the third strand of a ?12m raid on United.
A hitch over the move for Gibson, 23, isthought to centre on wage demands of around ?40,000 a week, but the Republic of Ireland international is ready to compromise.
O'Shea, meanwhile, looks set to join Brown at the Stadium of Light.
The 30-year-old utility man has made almost 300 starts for United and has five Barclays Premier League titles to his name, while he has become a stalwart of Giovanni Trapattoni's Republic of Ireland defence.
But while O'Shea is close to joining, question marks remain over Gibson, who has also attracted interest from Newcastle, with no agreement yet in place.
Big spender: Steve Bruce has been busy in the transfer market since the season ended
Bruce will hope for positive developments over the next 24 hours after a busy summer already, with Ahmed Elmohamady having made his loan move permanent and Connor Wickham,Craig Gardner, Ji Dong-won, Keiren Westwood and Sebastian Larsson having joined the club.
The players are back in pre-season training and Bruce is hoping that his squad will be boosted further by the time they play their first friendly at York next Wednesday. But there was one notable absence with 28-year-old Paraguay international midfielder Cristian Riveros having completed a 12-month loan deal with Turkish club Kayserispor.
Riveros has struggled to make an impression since his free transfer move from Mexican club Cruz Azul, and has made just 14 appearances. Bruce said: 'Cristian wants to play regular football and hopefully he will be able to do so in Turkey. We wish him all the best.'
Turkish delight: Sunderland have allowed Paraguay flop Cristian Riveros to move to Turkey on loan
Sunderland, meanwhile, have appointed legal director Margaret Byrne as the club's new chief executive following a restructuring of the board.
The Black Cats revealed that the 31-year-old, who they describe as 'a rising star in both legal circles and the football industry' will take over from Steve Walton, whose departure was announced on Wednesday. Chairman Niall Quinn said: 'Margaret has been a true driving force at the club since her appointment here more than four years ago and the fact that the club has gone from strength to strength on and off the pitch in that period is no coincidence.
The club has also appointed Bryan 'Pop' Robson as their new chief scout. The Sunderland-born former striker, who returns to Wearside from his last post as an international scout for Chelsea, played 174 times for the club during three spells, served as reserve-team coach and academy director and even stood in as caretaker manager.
He said: 'Sunderland is obviously a club very close to my heart. I had great times here both as a player and as a coach, so I'm thrilled to be back working with Steve Bruce and his excellent management team.'
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