Trossard, 27, is somewhat of a surprise name to have been linked with the Red Devils, with new manager Erik ten Hag looking to overhaul the current Manchester United squad.
According to Express, the 13-time Premier League winners and Newcastle are poised to make a move for Trossard, with the Belgian having impressed last season.
He made 35 appearances last campaign, scoring eight goals and providing three assists, and has made it into Belgium's recent UEFA Nations League squad.
Trossard scored two goals for his national side as Belgium beat Poland 6-1 and is starting to grow into one of the Premier League's most admired attackers.
A left winger who cuts inside and has often played behind two strikers at Brighton, Trossard is versatile enough to play for both the Red Devils and the Magpies.
The Belgian attacker joined Brighton from Genk in 2019 for £14 million and has since then gone on to make 104 appearances for Graham Potter's side, scoring 18 goals.
Manchester United and Newcastle United eyeing attacking influx this summer
Erik ten Hag is in dire need of attacking reinforcements, with the likes of Edinson Cavani, Paul Pogba and Jesse Lingard departing this summer.
The trio's contracts with the Manchester giants are expiring, and they are all parting ways with the Red Devils.
Hence, Ten Hag needs to improve his attacking options, with just Marcus Rashford, Jadon Sancho and Anthony Elanga the team's recognised left wingers.
Meanwhile for Eddie Howe at Tyneside, he oversaw a huge improvement at St James' Park after taking over in November. His team quickly climbed out of the relegation spot and finished the season in 11th place.
However, Newcastle have had their issues with a lack of goalscoring potency, with January signing Chris Wood managing only two strikes in 16 appearances.
Allan Saint-Maximin is Howe's first-choice left-winger. He has been one of the team's top stars since arriving from Nice in 2019 for £16.2 million.
However, perhaps Howe feels that the Frenchman needs competition to keep him on his toes heading into next season.
Saint-Maximin managed five goals and as many assists in 37 appearances across competitions last campaign.
Whether both Manchester United and Newcastle make their interest in Leandro Trossard concrete remains to be seen. However, both teams are eyeing attacking improvements this summer.