The 29-year-old Frenchman joined the Magpies from Eibar in the summer of 2017, but has struggled to nail down a role in Steve Bruce’s first-team plans.
Lejeune made just six Premier League appearances for Newcastle last season, with niggling injuries not helping his cause.
With the centre-half not in Bruce’s plans for the new season, he looks set to be on his way out of St. James’ Park.
Spanish La Liga club Alaves are looking to snap him up on a season-long loan deal.
The move going through would see the former Manchester City man return to Spain, where he has played for Villarreal, Girona and Eibar.
Lejeune has 36 La Liga appearances to his name and could be in line to add more to the tally in the 2020/21 campaign.
While the Frenchman appears to be on his way out, Bruce is claimed to want a new centre-back on loan this transfer window.
Newcastle were keen to sign Arsenal defender Rob Holding on loan but the Gunners have since decided to keep the Englishman as a back-up option, forcing the Magpies to look elsewhere.