Mali international Mahamadou Diarra will join Real Madrid on a five-year deal from French champions Olympique Lyon after the Spanish club agreed personal terms with the midfielder.
Real said on Sunday that the 25-year-old would be presented in the next few days after passing a medical with the club.
"He was the signing our coach ( Fabio Capello) had asked for because he considered him to be essential and so we are delighted that we are able to grant him his wish," said Real Madrid president Ramon Calderon on the club's Web site.
Neither club disclosed fee details but Spanish media say the nine-times European champions have agreed to pay Lyon some 26 million euros, making Diarra the most expensive close-season signing in the Primera Liga.
Lyon were originally reported to have asked for over 35 million euros for the Mali international but Calderon said they had settled for much less.
Diarra is the fourth player to join Real since Calderon was elected president last month and brings the club's total close-season spending to over 60 million euros.
Real have also signed Italy's World Cup-winning captain Fabio Cannavaro, Br azil midfielder Emerson from Juventus and Dutch striker Ruud van Nistelrooy from Manchester United.
A key figure in the Lyon midfield, Diarra joined the French side from Vitesse Arnhem in 2002 and has won the last four Ligue 1 titles with the club.
He will team up with Emerson to form a watertight partnership in the centre of midfield, a problem area for Real since French midfielder Claude Makelele left for Chelsea in 2003.
" Capello thinks he will be a key player in helping form a solid block in the centre of midfield where he will provide a lot of help to both Emerson and to the back four," said Calderon.
"He will help us correct our weaknesses of previous seasons. Capello has always said that we will concede very few goals this season and I'm really excited because I think he is a great player."
Diarra's arrival and the transfer deadline at the end of the month will accelerate moves for the club to offload players who are now considered surplus to requirements.
Central midfielders Pablo Garcia and Thomas Gravesen and right back Carlos Diogo top the list of likely departures, while sources at Real have said that the club is also mulling over offers from Serie A sides Inter and AC Milan for Br azil striker Ronaldo.
However, Real, who have not won a major trophy since 2003, have said that their spending has not yet finished.
They have expressed an interest in Arsenal forward Jose Antonio Reyes, although the search for another centre back is at the top of Capello's list of priorities.
"There's a week or so left until we finalise the squad and I think we will be able to provide the fans with another reason to celebrate before then," said Calderon.