Mikel Arteta’s team were 13 minutes away from their first Premier League defeat this season after Cole Palmer’s early penalty and Mykhailo Mudryk’s second-half goal put Chelsea in control.
But a miscued pass from Chelsea keeper Robert Sanchez allowed Declan Rice to give Arsenal a lifeline and Trossard bundled home the leveller with six minutes left.
Arsenal’s gritty comeback extended their unbeaten start to the league season to nine games, leaving them in second place behind leaders Manchester City on goal difference.
It was another display of the character and spirit pulsing through Arsenal over the last 18 months, qualities that are underpinning their bid to finally win the club’s first title since 2004.
“We didn’t play with enough purpose and clarity in the first half but the way we reacted was phenomenal,” Arteta said.
“I have no doubt about our character. I could see at half-time that we knew we had to do much better. I love that about the team. This is who we are.”
For Chelsea, it was a hammer blow after they were on the brink of delivering the first signficant victory of Mauricio Pochettino’s maiden season in charge.
The Blues have failed to beat Arsenal on home turf since 2018 and Pochettino said: “I’m disappointed because until the 77th minute we had the game under control against an amazing team.
“Mistakes can happen. It was unlucky because Arsenal’s first goal gave them belief. We need to know when to be calm and when to take risks. That will happen because we are still a really young team.”
Pochettino’s men took the lead in the 15th minute after William Saliba’s out-stretched arm blocked Mudryk’s header.
Chelsea’s penalty appeal initially looked set to be ignored, but referee Chris Kavanagh eventually awarded it after being advised by VAR to consult the pitchside monitor.
Palmer calmly drilled the spot-kick past David Raya to claim his second goal since signing from Manchester City earlier this season.
– Late surge –
Palmer was inches away from scoring again with a low drive that fizzed wide from the edge of the area.
Pochettino told Arteta not to go into coaching when the pair played together at Paris Saint-Germain, advice the Arsenal boss will be pleased he ignored.
The pair, who this week described their relationship as “like brothers” shared a warm embrace before kick-off, but there was little love lost between their teams.
Arsenal’s Bukayo Saka was singled out for some crude challenges by Marc Cucurella, while three players were booked in a feisty half.
Raya gifted Chelsea their second goal in the 48th minute when the Arsenal keeper failed to follow the flight of Mudryk’s miscued cross from the left flank as it drifted over his head into the far corner.
Mudryk’s fortuitous strike was also a painful twist for Arsenal after he spurned them to sign for Chelsea last season.
Raya has been preferred to Arsenal’s former first choice keeper Aaron Ramsdale in recent weeks, but has looked far from comfortable at times.
Raya’s confidence was shaken by his latest mistake and he almost handed Chelsea another goal with a wayward pass that Palmer intercepted but was unable to convert from 12 yards.
It was a crucial miss as Sanchez returned the favour in the 77th minute with a woeful pass that was seized on by Rice, who gratefully lofted his shot into the empty net from 25 yards.
Suddenly, Chelsea looked riddled with nerves and Arteta’s side made them pay in the 84th minute.
Saka curled a cross to the far post and Trossard got in front of Malo Gusto to slot home from close range.
Eddie Nketiah should have capped Arsenal’s remarkable late surge, but the striker fired wide from a golden chance to steal all three points.
Amazing
Arsenal Stages hit back to deny Chelsea in derby draw