Arsene Wenger’s manne started like a house on fire and looked good when they took the lead in the 31st minute through Theo Walcott.
The winger had just redeemed himself after wasting a chance from a penalty he had just won and they put his team on top.
But the Reds hit back through a brilliant Philippe Coutinho freekick to level the scores just before the break.
And it was all Jurgen Klopp’s team after the break as Adam Lallana fired the Reds into the lead five minutes in.
Coutinho made it 3-1 with another smart finish, before Sadio Mane gave the Merseysiders a three-goal lead.
The Gunners gave the visitors a scare when they pulled two goals back through Alex Oxlade-Chamberlain and Calum Chambers.
But the result meant Arsenal have now lost their opening home Premier League for the third season running.
And Wenger and his team got booed off by the fans after the first game of the season after failing to invest.