United have been tracking the Chilean u23 international for some time now and he trained at Carrington in March 2011.
Amidst reported interest from Man City, Sir Alex decided to make a move for the young attacker last month and he quickly completed a medical and was handed a work permit.
Henriquez, 18, helped Universidad to the Copa Libertadores semi final last season as well as the Chilean title scoring 11 goals. Whilst this is impressive for an 18 year old he faces a tough task in making an impression at Old Trafford with Robin Van Persie, Danny Welbeck, Javier Hernandez and the injured Wayne Rooney to compete with.
Sir Alex Ferguson said of Henriquez to ManUtd.Com:
“Angelo has made a tremendous impact on the game in his short career so far. His pace is a great asset and he reads the game really well for someone of such a young age.
“We have a proud record of developing young talent and Angelo fits the profile of a United player – skilful, attacking and someone who plays the game with real flair.”
“I am thrilled to be joining the biggest club in the world. Manchester United is a great team and has a great manager.
“To be able to be part of that is a huge honour and I can’t wait to get started. I hope I can be part of many successful years with United.”
Henriquez will be handed the number 21 shirt.