The Frenchman has been in superb form for the Eagles this season, with many pundits convinced he's now playing a final campaign at Selhurst Park ahead of leaving for bigger things this summer.
The Sun says United are interested, despite having young pair Josh Zirkzee and Rasmus Hojlund on the books.
United had top level scouts at Selhurst Park last weekend to watch Mateta, though their plans were scuppered after the player's ugly collision with Millwall goalkeeper Liam Roberts early into the FA Cup tie.
Mateta required 25 stitches to his head wound, though the injury won't be holding him back.
United see Sporting CP striker Victor Gyokeres as their prime summer centre-forward target, but Mateta is also gaining ground in discussions at Carrington.
For his part, Mateta is prepared to leave Palace for a bigger stage next season.