The Aston Villa captain is expected to replace Mason Mount, who has been forced into solitary confinement with his Chelsea teammate Ben Chilwell.
The news will delight England fans who have been clamoring for Grealish to have his chance, with the midfielder most likely to start in the No.10 position.
Grealish came off the bench in the draw against Scotland but, barring late changes, he will now get his first start in a major tournament for England, who have already qualified.
With Mount also in doubt to start England’s round of 16, tonight’s game represents a huge opportunity for Grealish to carve out a starting place for Southgate’s squad.
Harry Maguire is likely to start in the middle of defense in place of Tyrone Mings, as the Manchester United man works on a full game-changer.
It has also been suggested that Southgate is considering whether or not to offer a shock opportunity on the right to Bukayo Saka at Wembley tonight.
Phil Foden started both England group matches on the right side, but Southgate is considering a change of position with Saka competing against Marcus Rashford and Jadon Sancho.
Manchester City’s Kyle Walker is expected to return to the squad at right-back, while Shaw could keep his place on the left to play alongside his United team-mate Maguire.
Declan Rice and Kalvin Phillips are set to retain their place in the squad, with 17-year-old Jude Bellingham likely to be on the bench despite being one of the players put on hold when Mount was initially placed in administrative segregation.
Southgate has already confirmed that captain Harry Kane will start tonight and Raheem Sterling is expected to keep his spot on the left.