Champion Spanish shot stopper de Gea has refused to sign a new deal at Old Trafford, forcing the club to begin their hunt for a new gloveman.
English newspaper The Sun has reported that Ryan is believed to be at the top of United's goalkeeper hit-list, with his impressive performances at Brighton & Hove Albion lifting his stocks sky high.
United manager Jose Mourinho is believed to not be confident of keeping de Gea at the club beyond next season, hence their urgency to find a new 'keeper.
De Gea has long been linked with a move to Real Madrid, but Los Blancos' signing of Thibaut Courtois has all but ruined his chances of a return to his home town.
Although Ryan still has more than three years to run on his Brighton contract, the Seagulls would struggle to turn down a big offer should United come after the former Central Coast Mariners' number one.