Arsenal have booked their place in the Champions League last-16 after winning Group B by thumping Lens 6-0, but Manchester United's campaign is on life support after their draw in Turkey.
The Gunners had six different scorers in Wednesday night's (Thursday AEDT) London rout.
Kai Havertz, Gabriel Jesus, Bukayo Saka, Gabriel Martinelli and Martin Odegaard scored at Emirates Stadium as Arsenal became the first English club to lead by five goals at halftime of a Champions League match.
Jorginho converted a penalty in the 86th minute to round off the scoring for a team that has advanced with one game to spare, on 12 points.
"We had a chance to qualify today and we've done it in a really convincing way against a really good side," Arsenal boss Mikel Arteta said.
"It's great we're able to win in this way and we showed at home not to concede any goals and score a lot which is a positive factor. The players need to believe we can do that against big opponents."
Lens (five points) stay third and need just a draw at home to Sevilla (two) - who lost 3-2 in Eindhoven to PSV (eight) - in two weeks to finish in that position and seal a place in the Europa League's playoff round.
Earlier, United's hopes of reaching the knockout rounds suffered a huge blow after Erik ten Hag's men gave away a two-goal lead in a chaotic, thrill-a-minute 3-3 draw on an ear-splitting night against Galatasaray in Istanbul.
That result, combined with FC Copenhagen's 0-0 home draw with Bayern Munich leaves the Red Devils bottom of Group A on four points.
The German giants are already through on 13 points with the Danish and Turkish sides on five.
Alejandro Garnacho opened the scoring on 11 minutes before Bruno Fernandes rocketed the visitors further in the 18th.
Hakim Ziyech netted twice either side of a Scott McTominay goal before substitute Kerem Akturkoglu levelled with a 71st-minute scorcher.
"I think as a team we played very well," ten Hag said.
"We win and lose together ... I take many positives from this game.
"Of course, I am disappointed because we should have managed the game better, we will learn from that. Because this team is in development.
"Even after we had some setbacks, we kept going until the end and we should have won with big chances from Scott McTominay and (Facundo) Pellistri."
Elsewhere, runaway Group C winners Real Madrid beat second-placed Napoli 4-2 and Braga drew 1-1 with Union Berlin.
And the top two in Group D were also held, with Inter Milan coming from three down at halftime to draw 3-3 at Benfica while Real Sociedad and Salzburg finished scoreless.
Australian Associated Press