Herrera says this is a “dream move” and he cannot wait to pull on the famous red shirt.
Manchester United have announced that they have agreed to sign Spanish midfielder Ander Herrera from Athletic Bilbao.
The Red Devils will pay full price for the 24-year-old, after activating his buy-out clause, which was said to be worth £28.4m.
Herrera has signed a four-year contract, with an option to extend for a further year.
His move will be complete upon receipt of an international transfer certificate.
United assistant manager Ryan Giggs told the club’s official website: “Ander is a fantastic young player, with great energy and creativity.
“We believe him to be one of the brightest young prospects in Spain and I am certain he will be a big hit with the United fans.
“I’m delighted he has made the decision to come to Manchester and play his part in the club’s future. I’m looking forward to seeing him in action on our summer tour to America.”
Herrera added: “Signing for Manchester United is a dream come true.
“I have played at Old Trafford for Athletic Club in the UEFA Europa League and it was one of the highlights of my career so far.
“I have joined United to do all I can to help the team reach the club’s objectives. Having arrived on Tuesday, I’m excited to now be living in Manchester and I can’t wait for my first game in United’s famous red shirt.
“I will never forget my time with Athletic Club and I’d like to thank the fans and staff for all their support and, above all, wish all my fantastic former team-mates all the best for the future.”
Herrera played 33 La Liga games last season, scoring five goals and providing five assists.
He has been capped by Spain at three different youth levels, winning the UEFA European Under-21 Championship in 2011.
In 2012, he reached Bilbao reach the finals of the Europa League and the Copa del Rey. They lost to Atletico Madrid and Barcelona respectively.