England striker Alan Smith completed his move to Manchester United from Leeds United in a deal worth 7.05 million pounds ($12.81 million) on Wednesday.
The 23-year-old signed a five-year contract to become the Old Trafford club's first signing since the end of a disappointing season.
"I have never been more impressed with a young player, his desire to play for Manchester United is fantastic," United manager Alex Ferguson said in a statement.
"Certain young people come along with a special determination, and after speaking to him I expect that from Alan Smith. That desire will take him a long way".
Smith continued the exodus of players from cash-strapped Leeds, who were relegated from the English premier league this month, and his decision to join such bitter rivals is sure to anger his former team's fans.
"I have grown up at Leeds and spent some wonderful years there and I would like to thank everyone associated with the club," said Smith, who waived the signing-on fee he was entitled to in the transfer as a sign of goodwill towards his former club.
"Now I feel it's the right time to move on and there could be no better club than Manchester United," Smith added. "To be joining one of the best clubs in the world is fantastic and I am looking forward to the new challenges that face me."
The combative Smith joins strikers Ruud van Nistelrooy, Louis Saha, Ole Gunnar Solskjaer and Diego Forlan at Manchester United, who finished third in the premier league last season and failed to reach the Champions League quarter-finals for the first time since 1996.
Uruguayan Forlan is likely to be sold after an unsuccessful two-and-a-half year spell at Old Trafford, while speculation continues to link Dutch international Van Nistelrooy, United's number one forward, with Real Madrid.
Smith will hope to have a similar impact to the last striker to swap Leeds for Manchester, Eric Cantona.
The enigmatic Frenchman joined Manchester United in 1992, inspiring the club to their first league title for 26 years in his first season and sparking an era of domination of English soccer.
Leeds chairman Gerald Krasner explained the club's decision to allow Smith to leave just days after England goalkeeper Paul Robinson joined Tottenham Hotspur.
"We are beginning a major programme of rebuilding and restructuring at Leeds and we both believe his (Smith's) immediate future in football lies away from Elland Road," Krasner said in a statement.
"We know the feelings he has for our club and supporters and what it means to him to leave the number 17 shirt behind. We thank him for his service to Leeds and wish him well in his future career."
Smith, who has played eight times for England and is on stand-by for next month's European Championship, scored 56 goals in just over 200 appearances for Leeds since making his debut in 1998.
