The player is expected to join Napoli on a season-long loan with an option to buy the player's rights for €42 million.
The loan fee is estimated to be around €3 million.
Hojlund had a modest season with Manchester United, scoring only four goals in 32 Premier League appearances.
His departure from the club was made possible by the arrival of a new player, Benjamin Sesko, who was approved by the team's manager, Ruben Amorim.