The Swansea winger has joined for £15m, with the deal potentially rising to £18m with add-ons.
James becomes United’s first signing of the summer with more deals expected in the coming weeks.
The Red Devils confirmed the transfer on their social media channels this afternoon.
In one tweet, the club posted a photo of a smiling James at Carrington with the caption: “On a scale of 1 to @Daniel_James_97, how excited are you to see our new signing at #MUFC?”
But the replies show United supporters are divided when it comes to their new arrival.
“A solid 4,” one replied.
“ANNOUNCE Aaron Wan-Bissaka,” said another.
“He won’t get a game and will spend his time on warming the bench… Watch him in the Carabao cup thingy,” a third said.
“Want to see him play first, this is what u guys did to Sanchez and we have seen the outcome,” one wrote.
“I’ll be happier when we SELL Phil Jones, A.Young, the useless piano player and sack Ed WoodW*****.
However, some United fans are excited to see James in a red shirt.
“Very good young signing. Will play for the shirt,” one wrote.
“Buzzing!” responded another.
“10…. cant wait to see him flying up that wing,” one added.
Ole Gunnar Solskjaer is certainly delighted with his first signing of the summer.
“Daniel is an exciting young winger with lots of skills, vision, exceptional pace and a good work ethic,” he told United’s official website.
“He had a great season with Swansea City and has all the attributes needed to become a Manchester United player.
“We are delighted he has signed with our club and we are all looking forward to working with him.
“This is the perfect environment for Daniel to continue his development.”