After falling to defeat in the reverse fixture, the Gunners were set on revenge. They started the match as they meant to go on, with Kai Havertz opening the scoring within a quarter of an hour after poking home past Brice Samba.
Arsenal then went on to score a sensational three goals in six minutes, with Gabriel Jesus adding the second on 21 minutes after receiving the ball from Bukayo Saka, moving the ball onto his right foot and finishing calmly past Samba.
Gabriel Martinelli then put Arsenal out of sight, with the Brazilian brilliantly controlling a clearance from Takehiro Tomiyasu, driving with the ball from deep and then producing a fine curling finish.
Martin Odegaard added a fifth just before half-time, with the Norwegian volleying home a cutback from Tomiyasu to take his tally for the season to six goals and cap off a stunning first half display from Arsenal.
It was a second half that saw Arsenal slow the tempo and look to conserve their energy, however Jorginho was able to add a sixth in the 87 minute after converting a penalty following a hand ball.
Here are four things we learnt from the match:
Kai Havertz has endured a tough start to his Arsenal career after arriving for £60M from Chelsea in the summer. However, it now feels like the German has turned a corner with two goals in his last two matches.
He got Arsenal off the mark in the match and played with a noticeable boost in confidence, always making himself available to receive the ball and looking to make things happen.
It's a great sight to see him start to express himself and showcase his undoubted ability.
Another match, another brilliant Bukayo Saka performance, where he added another goal and assist to his tally. The England international now has 7 goals and assists in the UEFA Champions League this season, more than any other player.
His goal was slightly fortunate on the night, but Saka now always seems to find himself in the right place at the right time. His assist for Jesus' goal was trademark Saka at his best, cutting in from the right and somehow evading numerous challenges, before poking the ball through for the Brazilian forward to finish superbly.
Mikel Arteta will be over the moon that he was able to take Saka off just after the hour mark without the 22-year-old limping off.
It was a fantastic performance by the Brazilian, whose goal summed up what he can bring to the team. His trademark fake-shot followed by a sublime finish, put his side 2-0 up.
His work rate was as high as ever, dropping deep to win the ball back on several occasions and initiate attacks. For a player who has said that "goals are not his strong point", the 26-year-old did just fine on the night.
Another clean sheet for Arsenal. That's 3 in 3 at home in the Champions League this season.
William Saliba and Gabriel Magalhaes were faultless at the back again, with their physical presence towering over any rare Lens foray forward. The pair have formed one of the best centre-back partnerships in Europe.
They were rarely tested but in almost the last kick of the match Lens' Elye Wahi found space in the Arsenal box and unleashed a strike that was fantastically blocked by Gabriel, with the Brazilian celebrating the tackle as if he had scored a goal to keep his sides clean sheet in tact.