Manchester United have completed the signing of Dutch defender Alexander Buttner from Vitesse Arnhem, the club announced on Tuesday.
The 23-year-old has agreed personal terms and joins on a five-year contract until 2017.
Man Utd boss Sir Alex Ferguson told the club's official website: "Alexander is one of the best young left backs in Europe and we're delighted to sign him.
"He's someone we've been watching for a while now. He gives us some really exciting options in that position."
Buttner added: "Joining Manchester United is one of the best days of my life.
"It's a team I have admired for many years now and I can't wait to join my team-mates and play my part in helping the club be successful."