Manchester United has completed the signing of Netherlands defender
The 23-year-old has agreed personal terms and joins on a five-year contract until 2017.
United boss Sir
"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."
United States midfielder Robbie Rogers has signed for Los Angeles Galaxy - less than four months after he came out as gay and quit football.