The right-back, who turns 21 in October, played the full 90 minutes as Liverpool beat Tottenham 2-0 to claim a sixth European title on Saturday.
The result saw the Reds avenge last season’s Champions League final defeat to Real Madrid, a game which Alexander-Arnold also started.
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The previous youngster to start in two consecutive European finals was AC Milan’s Christian Panucci in 1994 and 1995 – the former Italy defender was 22 when he featured in the latter showpiece against Ajax.
Alexander-Arnold, who came through the ranks at Liverpool, played 11 games in this season’s tournament.
Speaking after Liverpool’s win over Tottenham, the England international told BT Sport: “It’s hard to even put into words what’s just happened.
“The celebrations that are going to happen tonight…
“The season we’ve had we’ve deserved it more than any other team. An early goal and a late goal has finished them off.