The Mirror reports that United boss Sir Alex Ferguson has outsmarted the Gunners in the race for the 17-year-old.
Fergie is ready to sign the youngster in a £10million deal. United will pay Southampton £5million up front and the rest of the fee depends on appearances.
Arsenal believed they had agreed a deal to sign Oxlade-Chamberlain, but the youngster now looks set to move to Old Trafford instead.