The Manchester United captain will reach the landmark in the Group B clash, as he has recovered from the illness that forced him off during the 6-2 opening-game victory over Iran.
After hitting the bar and provided an assist for Bukayo Saka in the resounding win, the centre-back has already enjoyed an eventful tournament.
"Harry's 50th cap is well deserved," said Southgate. "He has played a big role in two big tournament performances and we hope it's a third."
Maguire admits it will be a proud moment for him to join a select band of United men to play 50 times for the Three Lions.