The Guardian reports that United are ready to make a move for the 22-year-old in the January transfer window.
United boss David Moyes sees the young defender as the perfect long-term replacement for either Rio Ferdinand or Nemanja Vidic.
Mangala joined Porto from Standard Liege in 2011 for €6.5million.
United face competition from the likes of Chelsea, Manchester City, Monaco and Paris Saint-Germain in the race to sign the defender, who has a €45million buyout clause in his contract.
