The game seemed to be petering out to a draw until the 95th minute, when substitute Kalifa Coulibaly bravely headed in a winner for the Belgian side.
Read how it all unfolded in our minute-by-minute commentary below.
Thanks for joining me tonight for this tie from the Stade de Gerland. These two teams are currently in third and fourth place in Group H, but can both still qualify. We'll come to the ins and outs of that later, but let's get some team news first.
Lyon starting XI: Lopes; Rafael, Bisevac, Yanga-Mbiwa, Bedimo; Tolisso, Ferri, Malbranque; Valbuena, Lacazette, Ghezzal
Gent starting XI: Sels; Mitrovic, Asare, Nielsen; Foket, Renato Neto, Kums, Saief; Dejaegere, Milicevic; Depoitre
We'll start with the hosts, who have made four changes from the side that lost 3-0 to Nice at the weekend. Milan Bisevac comes in to replace Maxime Gonalons at centre-back, while Henri Bedimo is preferred to Jeremy Morel at left-back. Steed Malbranque starts in central-midfield, while Rachid Ghezzal will line up at left-wing.
Unsurprisingly, Gent have gone with the same starting XI that started their 1-0 win over Valencia in their last Champions League encounter. It's their only win of the group stage so far.
There has already been one Group H game this evening, with Zenit St Petersburg winning 2-0 at home to Valencia. It means that Zenit will win the group regardless of the matchday six results, but more importantly for these two teams, it means that both Lyon and Gent can still qualify.
It's simple enough for Lyon - only a win will do tonight. Anything less and they cannot reach the knockout stages.
Gent can afford to lose and still qualify for the knockout stages... but they would need to beat Zenit (who have a 100% record so far) and hope that Lyon beat Valencia. That makes it all a bit tricky, so I'm sure they will be targeting a win tonight so that their fate is in their own hands come matchday six.
Confused? Don't be. A quick glance at the Group H table should make it all a little clearer. You can look at the standings here.
We're just a few minutes away from kickoff, so there's time for me to have a punt on the scoreline. I think both sides will cancel each other out and I'm going to predict a 1-1 draw.
Incidentally, that was also the scoreline the last time that these two met. Gent ended the game with nine men, but still managed a 1-1 draw.
La Marseillaise is booming around the Stade de Gerland as a mark of respect for all those who lost their lives in the Paris atrocities less than two weeks ago. Very touching.
That was loud! An incredibly well-supported anthem this evening.
KICKOFF: Gent get us underway, kicking from left to right in their striking neon yellow kit.
Foket sends a ball down the line, but Yanga-Mbiwa scrambles across to shield the ball out of play.
Ghezzal sends an awkward left-wing cross into the box, but it's stabbed away by Nielsen.
It's Bedimo with another cross from the left wing from a deep position and it forces Mitrovic to clear for a corner on the stretch. However, Valbuena's cross is gathered by Sels with ease.
It's started in quite an open manner! No real chances yet but swathes of space in the middle of the park.
Dejaegere sends a low cross into the Lyon box from the right, but Lopes is alert and dives to his right to gather.
GOAL! (Jordan Ferri) Lyon 1-0 Gent
It's a dream start for Lyon, who must win tonight! Gent fail to clear a ball on the edge of the box and Ghezzal feeds it into Ferri on the left-hand side of the area. The midfielder opens his body up as though he is aiming for the far corner, but he wraps a right-footed finish in at the near post. Advantage Lyon!
Rafael sends Milicevic tumbling on the far touchline and Gent have the opportunity to swing a free kick into the box.
SAVE! Lopes stretches high to tip Saief's glancing header at the near post over the bar! A good response from the visitors.
CLOSE! The corner comes to nothing and Lopes sends a booming clearance down the pitch, which Lacazette chases down. He gets there ahead of Sels, but heads it against the Gent goalkeeper and it ricochets into the path of a visiting defender. Sels is a lucky boy there!
On second glance he's a very lucky boy. Lacazette's header hit Sels on the arm, which was raised above his head. Had the officials seen that, it would have been a red card.
Rafael takes aim after cutting in from the right, but drags his 25-yard shot wide.
Gent are just starting to grab a foothold in the game. They looked shell-shocked after conceding.
YELLOW CARD! Nielsen will be treading a fine line for the remainder of the game after scything down Ghezzal as the winger threatened to break down the left wing. No complaints from the defender.
Tolisso gives away a petulant foul on the edge of the box. He simply shoved Dejaegere in the back after the attacking midfielder had escaped him. A huddle of Gent players stand over the ball 30 yards out.
SAVE! Milicevic opts to cross, but Lyon clear and counter terrifically. Lacazette goes on the outside of his marker inside the Gent area and arrows a low shot towards the far corner which Sels tips behind.
Rafael attempts a header back to Lopes under pressure but gets it wrong and concedes a corner. It's taken quickly, but Lyon clear.
CHANCE! It's a huge chance for Dejaegere! Depoitre draws three defenders to him after turning on the edge of the box. The ball eventually breaks to Dejaegere, who is unmarked, but the attacking midfielder curls his shot from 18 yards over the bar.
Depoitre almost gets his head on a cross, but it's just too high for him and it sails out for a goal kick to Lyon.
YELLOW CARD! Neto is the second Gent player to earn a booking. It's another foul on Ghezzal and although I think it was clumsy more than anything, it was still probably worthy of a yellow card.
A switch of play enables Rafael to stand up Asare one-on-one, but the Brazilian simply gives it straight to the Gent defender. Poor decision-making from the former Man Utd man.
Milicevic gathers the ball in the left channel, but his first touch sends him wide and he blasts a high cross out for a throw-in on the stretch.
It's all become a little scrappy in the last couple of minutes.
UPDATE: Bayern are 3-0 up (of course), Messi has scored on his return to the Barcelona starting XI and both English sides lead 1-0.
Back in France, Gent have a chance to level with a free kick in a central area 25 yards from goal. Milicevic is standing over it again... along with about five teammates. What have they got up their sleeve?
GOAL! Lyon 1-1 Gent (Danijel Milicevic)
It's a sublime free kick by Milicevic! What a goal! Three Gent players stood facing the Lyon wall and charged at their opponents a couple of seconds before Milicevic struck the ball. It was all about the strike though. Milicevic's shot started way outside the near post before bending and curling into the top corner. Magnificent free kick!
The Lyon frustration is evident as Valbuena gives away a blatant foul before waving his arms and shouting at the referee.
Depoitre is penalised as he pushes off Yanga-Mbiwa when trying to reach a through ball. It looked a 50/50 challenge to me and the Gent striker would have been clean through if the whistle hadn't been blown.
Rafael sends a ferocious shot towards goal from a tight angle, which is batted away easily by Sels.
YELLOW CARD! Bedimo clips the heels of Depoitre and becomes the first Lyon payer to pick up a booking.
Ferri is now criticising the referee for giving a throw-in in Gent's favour. The hosts are riled.
Valbuena has been bright though and he wriggles free on the right before picking out Lacazette with a cross. The forward is beyond the near post and can only help on the cross, but there is no-one gambling on the far post and Gent clear.
SHOT! It's Valbuena again. This time he steps inside onto his left foot before hitting a low shot wide of the near post. Sels was never troubled, but Valbuena is finding a little bit of joy.
SAVE! Milicevic curls a right-footed cross into the box from the left wing and finds Dejaegere, who sends a glancing header towards the far post which Lopes parries behind for a corner. The header didn't have much pace on it but it needed saving.
Gent are ending the first half in the ascendancy and Lyon are at sixes and sevens at the back.
ONE MINUTE OF ADDED TIME
HALF TIME: Lyon 1-1 Gent
Lyon started brilliantly and went ahead inside 10 minutes through Jordan Ferri's strike.
However, Gent have been much the better side since then and thoroughly deserved their equaliser.
UPDATE: Elsewhere in Europe, Bayern Munich and Barcelona both lead 3-0 at the break. Surely one of those sides will win Champions League outright? Arsenal must win to keep their hopes of qualifying alive and they are 2-0 up at the break, while Chelsea lead 1-0 at Maccabi Tel Aviv.
Remember, Lyon must win tonight to keep alive their hopes of reaching the last 16. Can they find another in the second half? We'll find out soon.
This will be the last ever European game at the Stade de Gerland, as the hosts will move to the brand new Stade de Lyon in January. The home fans will be desperate to celebrate a victory one last time in their grand arena, but it doesn't look good so far.
KICKOFF: Lyon get us back underway knowing that they need another goal. A big 45 minutes for the hosts.
Lyon certainly seem to have started at a better tempo in this half. Lacazette tumbles as he tries to reach a through ball, but it was a desperate attempt by the French forward. Nothing doing.
BOOKING: Ferri is ruled out of Lyon's final group game after picking up a booking. His flailing arm caught Dejaegere in the face. It's very harsh, as he had no idea the Gent player was there.
Lovely build-up play by Gent ends with Kums sending a speculative ball much too far in front of Foket and Lopes strolls out to pick up the ball.
STAT: Gent have amassed 203 passes so far, compared to Lyon's 136. That definitely reflects the first half, which was dominated by the visitors.
SAVE! A deep cross finds Valbuena unmarked at the far post. The diminutive midfielder chests the ball down before firing a low volley towards the near post, but Sels gets down very quickly to grab the ball. Superb reactions.
A chance for Lyon to test Sels here as Rafael is fould right on the edge of the box by Milicevic. Valbuena and Ghezzal look very, very interested.
Ghezzal slams it into the wall and Ferri's subsequent attempt flies high over the bar. Poor on both occasions.
Lacazette lets out a blood-curdling squeal as he's fouled on the far touchline... but it's no shock to see him back on his feet joining the Lyon attack a few seconds later. You'd think he'd be embarrassed, wouldn't you?
SAVE! Ghezzal finds a pocket of space for himself 25 yards out and sends a shot towards goal, but it doesn't trouble Sels, who clutches the ball to his chest.
YELLOW CARD! It's a big decision for the referee, who hands Foket a yellow card after the wing-back brought down Lacazette, who was racing onto a through ball. I'm not sure how much contact there was - Lacazette went down theatrically - but this is a big chance for Lyon.
Valbuena's free kick kicks up off the top of the wall and goes out for a corner.
Half an hour left. Can Lyon find the winner that they need?
It's all a little too rushed and too tight when Lyon attack. They never seem to truly have the ball under control.
SAVE! Sels keeps his side level as he parries away Ghezzal's rising shot from 12 yards out at the near post. That was a big chance!
A wild, wild attempt by Neto, who clears the goal by at least 20 yards with a long-range effort.
SUBSTITUTION: It's a first change for Lyon, who bring on Darder for veteran midfielder Malbranque.
Gent were the better side in the first period, but Lyon have dominated to second period so far. They need a goal though.
Valbuena's teasing cross skips up off the surface and evades Mitrovic, but Lacazette can't take advantage as it flies past the striker.
SUBSTITUTION: Gent make their first change, as Saief makes way for Raman. Perhaps that sub was made with Saief's disciplinary record in mind. If the left wing-back had picked up a booking tonight, he would have missed the final group game.
Ferri blazes another long-range strike over the bar. In the build-up, a pirouette by Darder took him past two Gent defenders and drew a big cheer from the crowd. He's looked lively since his introduction.
Gent break and the ball comes to Depoitre in the left channel, but he takes a poor touch and is crowded out by Rafael and Bisevac.
Bisevac is there again to snuff out the danger as he covers and nicks the ball off the toes of Raman.
SUBSTITUTION: Lyon chuck on Beauvue with just over 15 minutes remaining, with Ghezzal making way.
Valbuena takes aim from range, but with the Gent defence backpedalling he can only fire high and wide.
YELLOW CARD! Kums picks up a booking for Gent.
Rafael hacks down Dejaegere after being nutmegged, but no further punishment is given.
While Lyon need a win, so do Gent. Victory tonight will put their fate in their own hands on the final matchday of the group stage. Looks like we're in for a nerve-jangling ending to the game!
Rafael grabs the ball after being fouled by Dejaegere... but the decision goes against him for handball! He's not happy!
There's a good battle going on between Rafael and Dejaegere! The Gent player is penalised for a foul this time, but Valbuena's deep free kick evades everyone.
Time is ebbing away for either side to find a winner. We haven't had any chances for a while either, but surely there will be one more before the final whistle?
Valbuena fires in a low cross which causes a little danger, but his second attempt - which is dinked to the far post - is miscontrolled by Bedimo.
CLOSE! A Gent corner causes havoc in the Lyon area and bobbles just wide of the near post after coming off the chest of Yanga-Mbiwa. He knew nothing about that.
Lacazette's through ball is slipped into the path of Darder, but Nielsen shows good strength to ease the midfielder off the ball.
SUBSTITUTION: It's a final throw of the dice for Lyon, who pin their hopes on 19-year-old Cornet. He replaces Ferri.
BOOKING! Lyon have a free kick in a dangerous position as Asare goes through the back of Rafael. It's on the right wing, just to the edge of the penalty area and 30 yards out. Can Valbuena deliver a good ball?
OFF THE LINE! The answer is yes! Gent scramble the first ball clear, but Cornet fires in a low shot from a tight angle which is hacked away by Rafinha with Lacazette lurking on his shoulder!
The Lyon crowd are trying to lift their side by singing La Marseillaise, but their side have looked a little insipid.
SUBSTITUTION: Gent wind down a few more seconds by bringing Coulibaly on for Depoitre.
FOUR MINUTES OF ADDED TIME: There's still plenty of time for a winner as Lyon come forward again.
Bisevac slices a poor clearance straight into touch. Not what Lyon need with very little time left.
YELLOW CARD: Raman picks up a silly booking for kicking the ball away as Lyon tried to take a quick free kick.
Lyon have been so, so poor in the final 15 minutes. That should be that as an aimless long ball goes all the way through to Sels.
It's a corner to Gent in the fifth minute of injury time. Surely not...?
GOAL! Lyon 1-2 Gent (Kalifa Coulibaly)
That goal has massive ramifications! First off, Lyon are definitely out of the Champions League. Secondly, Gent's fate is in their own hands come matchday six. Coulibaly won the first header, which bounced down into the ground. He reacted to power the second header against the underside of the bar and it ricocheted just over the line. It was brave, as he got a thwack in the face by Lopes, but he didn't care as he ran away in jubilation!
FULL TIME: Lyon 1-2 Gent
What a dramatic finale! A cruel, cruel blow for Lyon. The last ever Eurpoean game in the Stade de Gerland ends in defeat and their elimation from the group stage.
But what a story for Gent. It's their first season in Europe and they will definitely continue their European tour after Christmas. Whether that's in the Champions League or the Europa League depends on their result against Zenit in two weeks time.
It's a remarkable achievement which is being celebrated exuberantly by the Gent players on the pitch. They've made history and they deserve to celebrate!
Thanks for sticking with me right until the very end tonight. It was worth it! That's all from me though, but stick around on Sports Mole for plenty of reaction. Until next time!