The 25 players called up provide a mix of Premier League and Championship experience, although top flight regulars Tom Ince and Wilfried Zaha can only feature in the European Championship qualifier with Wales - having been born in 1992.
Manchester United's Jesse Lingard - who has spent the 2013/14 season on loan at Birmingham City and Brighton - and Championship player of the year Danny Ings also miss out on the France-based Toulon Tournament, which kicks off on May 21.
The tournament, which was introduced in 1967, is not run under UEFA supervision, although the 2014 edition will see storied countries participating; current champions Brazil feature alongside 11 time champions France, as well as appearances from Mexico, Chile and Portugal. One caveat of the tournament is the reduction of game time, with two 40-minute halves meant to challenge the mentality of young players in a new situation.
Southgate's options for his squad are limited, with a number of players unavailable due to either injury inclusion in the upcoming Championship play-off final and FA Cup Final.
Josh McEachran, once seen as the centre of a new, youthful Chelsea midfield, has been recalled to the squad, having not featured for the under-21's since last summer. The 21-year old has spent the season on loan at Watford and Wigan, and is available following the Latics 2-1 defeat to QPR in the play-off semi-finals.
19-year old Chalobah, who has featured for the under-21's 13 times since making his debut in 2012, also spent the season in the Championship. Fairly unremarkable spells at Nottingham Forest and Middlesbrough caused concern amongst Chelsea officials, with the midfielder struggling to improve upon the impressive season he had last season as a centrepiece in Watford's run to the play-off final.
Manchester United also have two players eligible for the tournament, with Michael Keane and goalkeeper Sam Johnstone in the 25 man squad. Defender Keane featured 13 times for Blackburn Rovers in 2014, as they made an impressive, but ultimately futile, attempt at securing a spot in the Championship play-offs. The Lancashire club finished the season two points off sixth place, and Keane contributed three goals in a series of strong displays.
The England under-21's are in action on May 19 as they face Wales in a European Championship qualifier, before beginning their tournament campaign with a game against Qatar on May 22.
The full squad for the Toulon Tournament is as follows (those in bold only available for Wales match):
Goalkeepers: Jonathan Bond (Watford), Jack Butland (Stoke City), Sam Johnstone (Manchester United).
Defenders: Tyias Browning (Everton), Eric Dier (Sporting Lisbon), Luke Garbutt (Everton), Ben Gibson (Middlesbrough), Michael Keane (Manchester United), Liam Moore (Leicester City), Brad Smith (Liverpool).
Midfielders: Nathaniel Chalobah (Chelsea), Jordan Cousins (Charlton Athletic), Jake Forster-Caskey (Brighton & Hove Albion), Josh McEachran (Chelsea), James Ward-Prowse (Southampton).
Wide: Tom Ince (Crystal Palace), Jesse Lingard (Manchester United), Jordan Obita (Reading), Nathan Redmond (Norwich City), Wilfried Zaha (Manchester United)
Forwards: Saido Berahino (West Bromwich Albion), Harry Kane (Tottenham Hotspur), Danny Ings (Burnley), Solly March (Brighton & Hove Albion), Cauley Woodrow (Fulham).