Holders Arsenal battled back from a goal down to secure a 2-1 first leg advantage in their Women's Champions League semi-final against Lyon at Emirates Stadium.
The Gunners, who beat Lyon in the last four last season on their way to Champions League success, trailed following Jule Brand's 18th-minute strike.
However, Lyon capitulated after the break as an error from goalkeeper Christiane Endler led to Ingrid Engen's own goal before another late mix-up between Endler and Engen led to Olivia Smith scoring into an empty net to give the Gunners a precious lead to take to France for next Saturday's second leg.
The loss is just Lyon's second defeat all season and their first defeat away at an English side in the Women's Champions League as Arsenal produced a huge result against the eight-time winners to continue their bid to retain the title they won last season.
Lyon broke the deadlock against the run of play in the 19th minute. Arsenal were caught in possession on the halfway line, with Brand sent surging forward down the left, past Kim Little and into the penalty area before firing beyond Daphne van Domselaar.
The home side went close in the 39th minute when Foord sent a header from a looping cross back across goal and just wide of the far post, but the Gunners were far from their best in the opening 45 minutes.
However, they were a different side after the break. They were given a penalty in the 51st minute when Little was sent tumbling under a challenge from Wendie Renard, but after a long look at the pitchside monitor, the referee ruled there had been a slight touch on the ball from the Lyon captain and overturned the decision.
Despite that, it didn't take Arsenal long to get back on terms as a blunder by keeper Endler then gifted them an equaliser in the 58th minute.
Mariona Caldentey swept in a low free-kick from the left, which drifted across the six-yard box. Arsenal forward Stina Blackstenius looked to dart in ahead of Endler, who failed to gather the ball which trickled on towards the far post. Lyon defender Engen then stabbed her attempted clearance against the woodwork and back over the line. After a VAR check for a possible block on Lyon defender Renard, the goal was given.
Lyon forward Kadidiatou Diani sent a rising drive against the crossbar in the 66th minute before Endler was then again at fault for Arsenal's late winner. The Lyon keeper and Engen collided as they both hesitated when dealing with a routine backpass into the penalty area, which allowed Smith to collect the loose ball and slot it into an empty net.
SSN reporter Anton Toloui at the Emirates Stadium:
"What a win for Arsenal - they were flat in the first half but a Rene Slegers rocket at the break made sure they came out swinging in the second.
"Lyon will still fancy their chances at home, fuelled by revenge for last season's 4-1 hammering at the same stage of the competition last season.
"Arsenal won the Champions League last season by coming from behind in the quarter and semi-finals.
"This season is going even better at this stage."
Arsenal manager Renee Slegers to BBC Sport:
"It's only half-time but if you look at the game, a lot of bits played out how we wanted it. There was a phase in the first half where we wanted more aggression in our press and I think we had some great solutions at half-time."
On the half-time talk, she added: "They spend some time with each other before we go in and Kelly Smith is normally there with the players. They have had a lot of conversations and it is all done in collaboration with the team. I think they were brilliant today. We got more pressure on the ball and we got more clarity on how we wanted to press and that was what we did with conviction in the second half and I want to thank the fans as well."
"We have a brilliant goalkeeper and a fantastic backline. We kept them away from our box and they had one shot on target and one corner was conceded."
Arsenal defender Leah Williamson to BBC Sport:
"I wanted to be back as soon as possible to help the team. I am glad I could contribute and share that load physically.
"First half was quite even, we gave away a cheap goal, but what you saw second half was a team on a mission, fuelled by the crowd.
"For us to give the fans a win and pay them back for their support is the nicest thing. It's a nice moment to celebrate."
On last season when Arsenal trailed heading to Lyon for the second leg of the semi-final, she added: "Last year we had a tough task and it rallied us together. I don't think the mentality will be too different.
"It's almost dangerous to compare, it looks the same, but so much is different now. Football changes so quickly. Every task is a new task.
"Intensity will be key. Lyon are giants of European football, they have a great crowd, like we do, so an intensity that matches that occasion and we have to be really clinical, defensively secure and... we'll see."
