The Red Devils are serious about securing the Brazilian from the Spanish giants.
According to multiple sources, United are hoping to sign the forward, who was not a regular starter for the La Liga club last term.
The sources suggest a fee for Cunha could be in the region of €50 million.
Atleti signed Cunha for only €30 million a year ago, with the club not eager to sell him.
The 23-year-old has seven senior caps for Brazil while he spent time in Germany before moving to Atleti.