✅ OFICIAL: El defensa Lejeune, aterriza en el Deportivo Alavés
— Deportivo Alavés (@Alaves) September 11, 2020
Lejeune will reunite with former Newcastle teammate Joselu as well as coach Pablo Machin, who trained him at Girona in 2014/15.
The former Manchester City player made just six Premier League appearances for the Magpies last season.
Lejeune has been hampered by injuries since arriving at Newcastle from Eibar in 2017.
The French centre-back now heads back to La Liga with Alavés for the 2020-21 season.