Portuguese teenage striker Cristiano Ronaldo signed for Manchester United for 12.24 million pounds ($19.64 million) from Sporting Lisbon on Tuesday.
The English premier league champions said the Madeira-born 18-year-old, whose full name is Cristiano Ronaldo dos Santos Aveiro, had signed a five-year contract.
"I am very happy to be signing for the best team in the world, and especially proud to be the first Portuguese player to join Manchester United," the English club quoted Ronaldo as saying.
"I look forward to helping the team achieve even more success in the years to come," said Ronaldo, who has played for Portugal at under-15, under-16 and under-17 level.
United manager Alex Ferguson said: "We have been negotiating for Cristiano for quite some time, but the interest in him from other clubs accelerated in the last few weeks so we had to move quickly to get him.
"It was only through our association with Sporting that they honoured our agreement of months ago.
"He is an extremely talented footballer, a two-footed attacker who can play anywhere up front, right, left or through the middle.
"After we played Sporting (in a pre-season friendly in Lisbon) last week the lads in the dressing room talked about him constantly, and on the plane back from the game they urged me to sign him -- that's how highly they rated him.
"He is one of the most exciting young players I've ever seen."
United, who have signed Cameroon midfielder Eric Djemba Djemba, French striker David Bellion and U.S. goalkeeper Tim Howard in the off-season, hope to complete their recruiting for the premier league season starting on Saturday with the signing of Brazil's Kleberson.
A club spokesman said United hoped midfielder Kleberson, who helped Brazil win their fifth World Cup last year, would sign later on Tuesday.
