Southgate did not name any wildcard options in his travelling party for the quadrennial tournament, meaning no room for Ryan Sessegnon or Jadon Sancho - two players reportedly in the manager's thinking.
Among the big-name absentees are Joe Hart, Jack Wilshere, Chris Smalling, Ryan Bertrand and Adam Lallana, the latter of whom has been included on the stand-by list, and Southgate has justified his decision to leave out some key men.
"I believe this is a squad which we can be excited about," he told the Football Association's official website. "It is a young group, but with some really important senior players so I feel the balance of the squad is good, both in terms of its experience, its character and also the positional balance.
"We have a lot of energy and athleticism in the team, but players that are equally comfortable in possession of the ball and I think people can see the style of play we've been looking to develop.
"The selection process has been over months really, it's not just been the last few weeks. We feel the team are improving and we want to continue that momentum.
"The first call-up for Trent Alexander-Arnold is well deserved. When we pick young players, it's not just because they are young, it's because their performances deserve it."