Asier Illarramendi has completed his move to Real Madrid, signing a six-year contract after passing his medical with the club.
The 23-year-old midfielder was unveiled at the club's Santiago Bernabeu stadium on Saturday, putting pen to paper on his contract alongside club president Florentino Perez.
The Spanish giants yesterday agreed to pay the midfielder's buy-out clause with Real Sociedad. The overall cost, made up of the clause and the associated tax penalties, to Madrid for the player is reported to be in the region of 39million euros (£33.6million).
The signing of the 23-year-old, who helped Sociedad earn a Champions League berth for the forthcoming season, is further evidence of Madrid investing in youth.
Illarramendi was a member of the Spain side which recently won the European Under-21 Championship in Israel.
He rose to prominence at Sociedad last season, playing an important role as they finished fourth in the Primera Division, securing a place in the Champions League in the process.
Illarramendi becomes Madrid's fourth signing of the summer - following the arrivals of Isco and Dani Carvajal from Malaga and Bayer Leverkusen respectively, while midfielder Casemiro's loan deal from Sao Paulo has also been made permanent.
The quartet will work next season under new Madrid boss Carlo Ancelotti, who has moved from Paris St Germain to replace Jose Mourinho.
Illarramendi, who was greeted by 4,000 fans, admitted his move to the capital was a dream come true.
"This is a very special day for me, this is a truly great club; a few days ago I would never have dreamt that I would wear a different shirt from that of Real Sociedad," he said.
"This is a unique opportunity for me, this is a truly great club and I will give my all for it. It was not an easy decision. I have had many wonderful moments in the 12 years I spent with Real Sociedad.
"I would like to thank everyone for their support. I accept this challenge eagerly and I promise you all that I will give everything I have for these colours; let's hope that next season will be one full of success Thank you to my family and friends for being there for me.
"Let us hope that the history of this club will continue to grow."
Perez, who sanctioned the big-money move, believes Madrid have marked their intent to plan for future.
"We have taken another step in our quest to bring in new talent," he said.
"This is a fantastic player who has come to Real Madrid; one of the brightest hopes of Spanish football.
"Today begins a great challenge for him. We are very happy to welcome Asier Illarramendi."
"We are constantly moving closer to sporting perfection in the quest for spectacular football that our manager Carlo Ancelotti is committed to, in our quest for new titles and for the realisation of the dreams of our supporters all over the world.
"We have a team with immense class but we are nevertheless convinced that we have to keep working intensively to strengthen even further the model that has made Real Madrid the greatest team in the history of the game."