After Three Lions appearances for Aaron Kuhl, Jake Cooper, and Jordan Obita in recent years, the Royals' 18-year-old shot-stopper has been picked for Aidy Boothroyd's 24-man squad.
The goalkeeper has been a mainstay in Reading's Under-18 side in 2015/16, reaching the Youth Cup quarter-finals and finishing seventh in the league.
Southwood will hope to be involved as England face Mexico in a double header on June 4 and 6, both taking place at Centro de Alto Rendimiento, with the summer U19 European Championship in mind.
Joining the academy product in the squad are Premier League players Cameron Borthwick-Jackson of Manchester United, West Ham's Reece Oxford, and Liverpool's Sheyi Ojo, who appeared in the Reds' last day trip to West Brom.
May 16 is, of course, a special day in terms of Reading goalkeepers getting the nod from England. Three years ago to this day, Alex McCarthy was handpicked to join the squad for the Maracana-opening friendly with Brazil.