The Belgium youth international has signed a contract that will keep him at Old Trafford until June 2030.
His first interview is available to watch now, exclusively for MUTV subscribers until 20:00 BST on Tuesday, before its wider release.
It’s not certain when we’ll first see Lammens feature for Ruben Amorim’s side, but his jersey number has already been confirmed.
The no.31 has been worn by some big names in the past, including Nemanja Matic, who had it throughout his United career, and Bastian Schweinsteiger.
Marouane Fellaini held it for two seasons, before switching to no.