Southgate has selected a young group, which includes the uncapped Alexander-Arnold - a likely starter for Liverpool in next week's Champions League final against Real Madrid - and Chelsea starlet Loftus-Cheek, who boasts just two previous senior appearances.
As well as leaving out Hart following the West Ham United loanee's loss of form, Southgate has also omitted Arsenal midfielder Jack Wilshere and Liverpool's Adam Lallana, while Ryan Sessegnon, Ryan Bertrand, Chris Smalling and Jonjo Shelvey fail to make the cut.
England start their Group G campaign against Tunisia on June 18, before games against Panama and Belgium.
England's 23-man squad in full:
Goalkeepers: Butland, Pickford, Pope
Defenders: Alexander-Arnold, Cahill, Delph, Jones, Maguire, Rose, Stones, Trippier, Walker, Young
Midfielders: Alli, Dier, Henderson, Lingard, Loftus-Cheek
Forwards: Kane, Rashford, Sterling, Vardy, Welbeck