The Blaugrana scored four quick goals in quick succession, including a splendid strike from Lionel Messi to win Barcelona first trophy since 2019.
Barca was disappointed until the 60th minutes when Antoine Griezmann sent in Frenkie de Jong’s cross before De Jong himself headed in after three minutes.
Messi at that point drove from his half, passed the ball to De Jong twice before finding the back of the net for Barca’s third.
Messi added another four minutes later, clearing in Jordi Alba’s cross.
Triumph gives Barca their first trophy under Ronald Koeman and their first trophy since 2019.
For Athletic Bilbao, it was the second Copa del Rey final loss in about fourteen days after they lost to Sociedad in the postponed 2020 final on 3 April.