Trippier, naturally a right-back, has been preferred to left-footers Ben Chilwell and Luke Shaw, with manager Gareth Southgate counting on his delivery from set-pieces.
Raheem Sterling and Phil Foden start alongside captain Harry Kane in the attack, with Jack Grealish named among the substitutes.
Chilwell and Jadon Sancho miss out on a place in the 23-man squad, though neither player is injured. All Euro 2020 teams are required to name three goalkeepers in their squad, with two on the bench.
As expected, Harry Maguire also misses out after failing to recover from an ankle injury in time. Jordan Henderson is on the bench having only recently returned from a groin problem.
Kalvin Phillips partners Declan Rice in midfield, while Tyrone Mings starts alongside John Stones in defence in Maguire's absence.
The inclusion of Trippier over Chilwell and Shaw is a surprise, despite Southgate talking up the Atletico Madrid’s full-back’s versatility during the build-up to this tournament.
Chilwell did not play in either of England’s pre-tournament warm-up games against Austria and Romania after playing in and winning the Champions League final with Chelsea and joining up with the camp late.
Shaw started against Romania but was also a late arrival after Manchester United’s Europa League final defeat to Villarreal.
England: Pickford; Walker, Stones, Mings, Trippier; Phillips, Rice; Sterling, Mount, Foden; Kane.
Substitutes: D. Henderson, Johnstone, Shaw, Grealish, Henderson, Rashford, Coady, Calvert-Lewin, White, James, Saka, Bellingham.
Croatia: Livakovic; Gvardiol, Caleta-Car, Vida, Vrsaljko; Brozovic; Perisic, Kovacic, Modric, Kramaric; Rebic.
Substitutes: Kalinic, Sluga, Brekalo, Vlasic, Budimir, Pasalic, Skoric, Badelj, Petkovic, Juranovic, Bradaric, Ivanusec.
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