The 21-year-old midfielder joined the Red Devils in 2019 but has failed to earn minutes on the pitch during his stay at Old Trafford which had led him to a move away.
Burnley have reportedly snapped up the youngster for a £5.4m fee, potentially rising to £9.4m with add-ons.
The midfielder scored just once in his 10 senior appearances for the club and had spells on loan with Birmingham City and Sevilla.
He spoke about the move and how manager Scott Parker convinced him about Turf Moor.
“I’m very excited. I'm very happy to be here and I can’t wait to see the fans. I have played against Burnley before at Turf Moor and the atmosphere was amazing.
“After speaking to the coach (Scott Parker) the project sounded good to me and hopefully we can make success.”