The 30-year-old Frenchman joined the Magpies from Eibar in the summer of 2016 and made 24 appearances as United finished tenth in the Premier League.
Unfortunately, the 2017/18 campaign saw him suffer two anterior cruciate ligament injuries but he recovered to score his first two goals for the club in a stunning comeback at Everton in January 2020, before heading to La Liga with Los Babazorros on a temporary basis last term.
Lejeune made 46 appearances in all competitions for Newcastle. Everybody at the club wishes him well for the future.