Barcelona blitzed Arsenal 4-1 on Tuesday as the holders kicked their Champions League campaign off in style at the Estadi Johan Cruyff.
Mariona Caldentey, Alexia Putellas and Asisat Oshoala were all on target as Barça raced into a three-goal lead early in the second half.
Frida Maanum pulled one back for Arsenal but substitute Lieke Martens added a fourth to seal the three points for Barca late on.
Alexia missed the chance to make it five in stoppage time when she saw a penalty saved by visiting goalkeeper Manuela Zinsberger.
Barca, who beat Chelsea in last season' final, were far too good from the start and the only surprise was it took them 30 minutes to open the scoring.
Oshoala's long range effort was spilled by Zinsberger and Mariona was in the right place at the right time to give the European champions the lead.
The second goal followed soon after. Oshoala was played through and the Nigerian striker squared for UEFA Player of the Year Alexis to score from close range.
Oshoala added the third after the break and Aitana Bonmati should have made it four before Arsenal finally had their first spell of pressure.
The Gunners, who are top of the league in England, came close through Nikita Parris, who had a shot stopped on the line by Mapi Leon.
Moment later, Arsenal did have a goal. Tobin Heath's free-kick found Maanum in the box and she turned the ball over the line.
That scare woke Barca up and substitute Martens began to make inroads on the Arsenal defence.
The Dutch forward had already come close when she eventually added the fourth, dinking the ball over Zinsberger after displaying good strength and pace.
Alexia missed the chance to add a fifth from the spot late on but her miss did little to take away the gloss from another assured performance from the Catalan side.
They return to action in Europe next week at HB Koge as the Women's Champions League features a 16-team group stage for the first time.