English publication 'The Daily Mail' reports that the 16-year-old has been a target for United for over a year after he impressed playing against them for the Portuguese side.
Spanish giants Real Madrid had also been linked with a move but it is thought that United have won the race for his signature after agreeing a deal with Befica.
Embalo was born in Bissau, Guinea though he represents Portugal at youth level. The youngster has scored 15 goals in 18 games for Portugal U17s.
He generally plays on the right, cutting in onto his stronger left foot and is renowned for his pace and trickery.
The young forward has been compared to former United winger Angel Di Maria, though he will be hoping his Old Trafford career is more successful than the Argentine's was.
Manchester United's chief scout Javier Ribalta and head of development John Murtagh are both thought to have watched the player in action for Benfica's U19s against United last month in a game that ended 2-2.