The Spanish player has signed a 4-year contract with an option for a further year after completing his switch to Old Trafford.
United's move for Athletic Bilbao midfielder Herrera has been the polar opposite of the whirlwind affair most clubs would want to conclude their business in.
Stretched out over a couple of years, the Spaniard has been on the Old Trafford club's radar for some time, and previous moves for the player have broken down just when a deal seemed inevitable.
Even this summer, 'the is it done, isn't it done' nature of the transfer would have likely worn fans' patience thin and seems to have sent the transfer fee soaring.
But now the deal is done, and it took a last minute intervention by the player himself to push it over the line. The player was pictured with Sir Bobby Charlton and the club shirt after the transfer was confirmed.
On Wednesday, Athletc officially rejected a near £29 million offer for the 24-year-old, though Sky Sports News reporter James Cooper revealed it was likely to just be posturing by the La Liga club to avoid looking like they let their players be poached easily.
One of the reported sticking points in the deal had been Herrera's buyout clause, supposedly set to rise on July 1st, something that has been solved by the player paying off a portion himself in order to seal the move.
The Spanish side posted confirmation of this on their website today, stating: "The Athletic Club thanks Ander Herrera for his dedication during the three seasons he has enjoyed the club and wishes him the best in his future sports projects."
The Mail revealed that Herrera had been given a tour of United's training ground yesterday, after presumably undergoing a medical and discussing personal terms with the famous English side.
Now the last few details have been agreed between United and Athletic, it looks like Louis van Gaal's first big signing is finally in the bag.