United have announced the arrival of Wales international Daniel James from Swansea for an initial fee of around £15m.
James has signed a five-year contract with the Old Trafford club, becoming the first signing for Ole Gunnar Solskjaer since he took over from Jose Mourinho.
The 21-year-old scored five goals in 38 appearances during a breakthrough 2018-19 season with Swansea.
“This is one of the best days of my life,” James said.
James, who lost his father last month, started both Wales’ two recent Euro 2020 qualifying matches against Croatia and Hungary.
He scored his first international goal on his debut in a 1-0 win against Group E opponents Slovakia in March.
“This is an incredibly proud moment for me and my family. However, it is tinged with sadness that my father isn’t able to share this experience with us,” said James, who nearly joined Leeds United in January.
United finished sixth in the Premier League last season and will be playing in the Europa League next season.
“Daniel is an exciting young winger with lots of skills, vision, exceptional pace and a good work ethic,” said Solskjaer.
“This is the perfect environment for Daniel to continue his development.”