Barcelona may well have expected a tricky trip to Girona, given that they upset the applecart by qualifying for the Champions League last season, but inspired by Lamine Yamal, they ran riot.
On the half-hour mark, Barcelona found a way through thanks to wonderkid Yamal, who robbed defender David Lopez on the edge of his own box, turned, and finished coolly.
And he had a second just six minutes later, curling an effort into the bottom corner from the edge of the box, through a clutch of Girona bodies.
Girona thought they had a penalty before half-time, as the ball struck Inigo Martinez's hand, but the referee was overruled by VAR and the decision was amended.
Within two minutes of the second half, Barca were 3-0 up, as Dani Olmo finished viciously from an acute angle.
Just after the hour, Pedri added a fourth, sprinting onto a brilliant through ball from Marc Casado and lifting the ball over the goalkeeper.
Girona pulled a goal back in the final 10 minutes through Christhian Stuani, while Ferran Torres was sent off before full-time after a nasty lunge in midfield.
GOAL rates Barcelona's players from Montilivi...