The champions had slipped to second in the table after AS Monaco's 2-1 win over Lyon earlier in the day, but could leapfrog their title rivals with a victory against Les Verts at Stade Geoffroy-Guichard.
In an incident-packed game, PSG came from behind to snatch a late draw against 10-man Saint-Etienne to edge back to the top.
Read how it all unfolded in our live commentary below.
7.31pmGood evening and welcome to Sports Mole live Ligue 1 coverage from the Stade Geoffroy-Guichard where Saint-Etienne host Paris Saint-Germain.
7.33pmIt's the final match from France of the weekend, but it is no doubt the biggest. Paris Saint-Germain will return back to the summit of Ligue 1 with a victory tonight, but they have to win at Saint-Etienne, which is something they have found very difficult according to the history books.
7.35pmLes Parisiens, who are still unbeaten so far this term, have begun to play a far more fluid and entertaining style of football under Laurent Blanc than under his predecessor Carlo Ancelotti, which has had spectators in awe and, at times, the rest of the world surfing YouTube to witness their greatness - note Zlatan Ibrahimovic over the past week.
7.35pmThey bought well in the summer too. While £55m Edinson Cavani is obviously one of the deals of the window, young duo Lucas Digne and Marquinhos, a left-back and a centre-back respectively, proves that the club aren’t just thinking about the present but also forecasting the future, and those two should be big hitters for years to come. The latter of the two has already featured heavily following the injury suffered by captain Thiago Silva, and has shown why Blanc was willing to spend around £30m on the 19-year-old.
7.36pmHaving drawn their opening two matches (they failed to win any of their first three last season), PSG have started to show what they are capable of and talismanic striker Zlatan Ibrahimovic is beginning to find his top form, with 10 goals in his last five games in all competitions.
7.36pmThey drew with title rivals AS Monaco, but managed to secure a good win over Marseille in Ligue 1, as well as smashing Olympiacos, Benfica and Anderlecht in each of their first three Champions League games. The scary part is that the champions now head the division by two points, but Blanc is still unsure of his best formation and team, and they haven’t gotten out of third gear yet.
7.38pmSaint-Etienne, after losing star man Pierre-Emerick Aubameyang to Borussia Dortmund prior to the campaign, have been there or thereabouts at the top of Ligue 1, and sit ninth prior to this match, having been without a recognised striker for most of the season.
7.38pmHowever, big Brazilian forward Brandao has now returned from injury and given them a focal point in attack, which the likes of Jeremy Clement, Renaud Cohade, Romain Hamouma and Fabien Lemoine thrive off.
7.38pmGoalkeeper Stephane Ruffier and centre-back Kurt Zouma are also two of the divison’s standout players, so they have a solid team that can give anyone a run for their money. Les Verts have lost to Lille, Marseille and Monaco this year, who they will be hoping to be battling it out with come the end of the year. However, with Brandao back, they could crack on from this weekend and return to the summit of the division.
7.39pmIf we focus on this fixture though, these two teams met three times last year, with PSG failing to taste victory in any of them, including a defeat in a penalty shootout in Coupe de la Ligue.
7.40pmLast season, PSG were unbeaten heading into matchday 11 before they lost that streak to Saint-Etienne. By the way, tonight marks match number 11 of the Ligue 1 season. Coincidence? Blanc will certainly hope so.
7.42pmBefore we get into more detail, let's have a look at the teams.
7.49pmPSG XI: Sirigu, Van der Wiel, Marquinhos, Alex, Maxwell, Matuidi, Verratti, Motta, Lavezzi, Cavani, Ibrahimovic
7.50pmLaurent Blanc has stuck with the same starting XI that battered Anderlecht in the Champions League during the week.
7.51pmMy guess is that Blanc is going for a 4-3-3, with Cavani on the right, Lavezzi on the left and Ibrahimovic through the middle. However, it isn't out of the question that Blanc goes for a 4-4-2 and puts Matuidi and Lavezzi on the wings, leaving Cavani to partner Ibrahimovic upfront. However I would expect it to be the former.
7.57pmLooking at their recent form, Saint-Etienne currently possess a very leaky defence, while PSG are scoring for fun. It's a real history vs. from kind of fixture tonight.
7.59pmPSG are enjoying the best start to a season to the Ligue 1 campaign since Olympique Lyonnais in 2006-07 and are haven't lost in 21 domestic matches since a 1-0 loss at Reims in March. It is their longest unbeaten streak since a record 27-game stretch during their title-winning 1993-94 campaign. They are currently looking to make it seven wins on the spin.
8pmLes Verts have conceded 13 goals in their last eight Ligue 1 games and recent results have suffered as a consequence. They had taken just one point from four outings prior to the international break before bouncing back to beat Lorient 3-2 at home last weekend.
8.01pmThe two teams have made their way out at the Stade Geoffroy-Guichard. Saint-Etienne is their home kit of green shirts, white shorts and green socks, while PSG sport their traditional first strip with navy shirts with red and white squares, navy shorts and socks.
8.02pmLaurent Blanc takes charge of PSG against the club he used to play for, while Blaise Matuidi and Jeremy Clement also line up against their former employers.
1 minKICK OFF! Saint-Etienne, playing from left to right, get the first half started.
3 minBrilliant noise inside what is known as the Green Cauldron. The home fans will need to get behind their side if they are to get a result here. They are more than capable of it.
4 minIbrahimovic turns on the left edge of the box and stabs a dipping cross towards Cavani at the far post, but it's just too far ahead of his teammate.
5 minBrandao will be a key man for Saint-Etienne tonight. Les Verts form dipped when the big Brazilian got injured, but he is back in the team now and adds another dimension to their attack.
6 minA lot of boos for Ibrahimovic from the home fans as he catches Ghoulam. The left-back actually looks to have followed through on his clearance and struck Ibrahimovic before making a meal of it.
7 minYELLOW CARD Brandao is booked for a challenge off the ball. Both teams have a player down and tempers are flaring early.
9 minCertainly no lack of action in the opening stages of the match, although neither keeper has had anything of note to do yet.
10 minCHANCE! Big chance for Saint-Etienne. Brilliant link-up on the left between Ghoulam and Hamouma, the latter cuts the pass back to the edge of the six-yard back, but Brandao gets right underneath the ball and skies it over at the near post.
12 minIt's been a good game so far, with end-to-end action. Both sides keen to attack.
16 minCHANCE! Good work from Corgnet, who dispossesses Thiago Motta before racing to the edge of the D, but his shot is cut wide of the far post.
18 minGOAL! Saint-Etienne 1-0 Paris Saint-Germain (Benjamin Corgnet)
18 minThe hosts are in front, and Marquinhos is the man to blame for PSG here. His clearance is awful and falls to the feet of Hamouma on the right of the area. He runs inside and lays it off to Corgnet. His first touch isn't great, but the ball pops up nicely for him and he slams it into the corner. No chance for Sirigu. Saint-Etienne lead.
20 minNearly a leveller for PSG, as Ibrahimovic competes with three Saint-Etienne players for an aerial pass. Ruffier can punch behind (after smashing Zouma in the face) for a corner.
21 minThe corner falls on the edge of the box to Matuidi, who hammers a low shot towards the bottom corner, but it deflects out for a corner.
22 minRuffier does brilliantly well to collect the resulting corner, although he was fouled anyway. Galtier, meanwhile, is getting a talking to from the referee.
23 minCorgnet with a solid knee to the back of Verratti's legs with leaves the Italian down in pain. Now he knows how it feels. No card, despite PSG protests.
26 minPSG have thrown a few crosses into the box, but Saint-Etienne have dealt with them well so far. Lavezzi did ever so well to beat his man and run up the byeline before crossing just then, but Perrin was on hand to make the block and clear.
29 minCLOSE! Saint-Etienne causing a lot of problems down the left. Again it's Hamouma who weaves his way down the wing before passing it back to Brandao. The striker takes a touch and hits it towards the bottom corner, but it's just wide.
31 minOFF THE BAR! What an awesome goal this would have been. The ball sits up nicely for Lemoine about 30 yards out, and he cracks a half-volley which has Sirigu beaten, but it dips onto the top of the crossbar. So unlucky.
32 minYELLOW CARD Alex goes into the book for a late challenge.
34 minLavezzi is tripped 30 yards from goal to the left of centre, and PSG have a free kick from the sort of position that Ibrahimovic slammed one in from against Anderlecht.
35 minIbrahimovic has a go and gets his laces through it, but it drifts wide of the far post.
38 minYELLOW CARD Lavezzi is breaking away at pace before being hacked down by Lemoine. He's taken the hit for the team there for what insiders seem to call a 'smart' booking, although you're never supposed to admit that.
39 minGreat cross into the box by Mollo which PSG scramble behind for a corner.
40 minCHANCE! Great corner in from Saint-Etienne, and Perrin gets a powerful head to it which flies just wide. They're pushing for a second before the break.
41 minSaint-Etienne are really up for this and are not afraid to take it to Les Parisiens. PSG have been a shadow of their recent form in this match. They're not being given a chance to play their own game.
42 minYELLOW CARD Hamouma gets a finger in the eye as he beats Maxwell, which lands the Brazilian a yellow.
46 minKICK OFF! PSG, playing from left to right, get the match back underway.
47 minSaint-Etienne with an early corner which Mollo takes from the left, Zouma goes for it but can't get significant contact on the ball to create a chance.
48 minVerratti is fouled by Mollo on the edge of the box, giving PSG a great position for a free kick. Ibrahimovic is over it, right on the edge of the D, dead central.
49 minCLOSE! It is Ibrahimovic who opts to smash it towards the bottom corner. He gets incredible speed on the ball, but it flies wide of the near post.
51 minGOAL! Saint-Etienne 2-0 Paris Saint-Germain (Romain Hamouma)
51 minMy word that is shocking defending from PSG, and they have a job on their hands now. Sirigu comes to catch a cross but drops it, the ball falls to Hamouma on the edge of the box, who guides a slow shot towards goal, but none of the PSG defenders can clear it.
54 minCLOSE! PSG showing some more urgency as Ibrahimovic scoops a pass over the Saint-Etienne backline. It falls to Matuidi, who turns and smashes the ball, but if fizzes wide of the far post. Difficult chance, but that's more like it from the champions.
56 minCould this be the end of PSG's unbeaten record? It's looking that way. They have 35 minutes to turn it around.
57 minNeedless to say, the home fans are in delirium right now.
58 minLemoine, who is down with blood pouring out of his head, looks as if he is going to be sent off for a deliberate foul, thus earning his second yellow.
59 minRED CARD! Fabien Lemoine is duly sent off, and now PSG have a chance to get back into it. Lavezzi had beaten Lemoine all ends up, and the Saint-Etienne man pulled him down to avoid the danger. Lavezzi caught Lemoine with an elbow on his way down, hence the blood, but Lemoine is off.
60 minYou don't need me to tell you that this game is getting feisty. That is, of course, unless you are nowhere near a TV and only have me to help you through the game. In which case, the game is getting feisty.
61 minMotta sprays a ball out to Maxwell on the left of the box, who lobs a cross to the near post to Lavezzi. The winger puts a weak header straight at Ruffier, and he should have done better.
63 minPSG CHANGES Lucas and Jeremy Menez have come on, in place of Ezequiel Lavezzi and Alex.
63 minSAINT-ETIENNE CHANGE Ismael Diamonde, a defensive midfielder, replaces the goalscorer Corgnet.
64 minWith those changes, Blanc thinking attack, whereas Galtier is thinking preserve.
65 minPSG are on the offensive now, and Ibrahimovic wants a penalty after walloping an effort at goal which cannons off the body of Zouma. The defender is fortunate to be conscious after that hit.
67 minSAINT-ETIENNE CHANGE Max Gradel, the former Leeds United man, is on in place of Mollo.
68 minGOAL! Saint-Etienne 2-1 Paris Saint-Germain (Edinson Cavani)
68 minWhat a finish to this game we're going to have. PSG work a corner really well which results in Maxwell being threaded through on the left of the box, before crossing for Cavani to flick the ball in at the near post. Game on!
69 minYELLOW CARD Menez goes into the book for a trip on Menez.
71 minSAVE! Lucas hits a shot from range which Ruffier doesn't see until late, but manages to keep it out with his feet.
72 minStrap on your seatbelts for this final 18 minutes, it's going to be one-way traffic you would have thought.
73 minYELLOW CARD Perrin intercepts a pass on the edge of his own box and races forward. He takes a heavy touch which allows Marquinhos to come into play, but the Saint-Etienne man, despite getting a lot of the ball in the tackle, floors the Brazilian and sends him flying to pick up a booking.
76 minPSG are forced into being patient here. Menez tees up Ibrahimovic, who blasts an effort off the back of Perrin and out for a corner.
77 minPSG CHANGE Adrien Rabiot is on for Verratti.
78 minSAINT-ETIENNE CHANGE Brandao, who has cut an isolated figure since Lemoine's sending off, is swapped for Franck Tabanou.
80 minSaint-Etienne were temporarily down to nine men for a moment then as Zouma was off the field receiving treatment. The crowd did their nut when the referee refused to allow him back on the field while PSG went of the attack. Nervy times.
82 minPSG continue to be patient, before Van der Wiel passes inside to Matuidi. He paces forward before having a go at goal, but he spurs his shot high and wide after striking Hamouma's shin on the way through.
84 minMenez drives at the heart of the Saint-Etienne defence and is about to shoot, but Zouma makes a wonderful block to concede the corner.
85 minCHANCE! The corner is played to the far side where Lucas whips a cross back into the mix. Thiago Motta rises highest at the far post, but he couldn't keep his header down as it flew over.
86 minCLOSE! Saint-Etienne nearly kill the game. Ghoulam dips in a venomous corner from range which bounces just in front of Sirigu. The keeper can save the effort without knowing too much about it, before Gradel skies the rebound. Big opportunity.
88 minAs things stand, PSG will stay second, a point behind AS Monaco, while Saint-Etienne will climb to fifth.
90+1 minCHANCE! Great run from Lucas, he can't see a pass so he twists and turns to adjust his footing before firing a low effort across goal from the edge of the box which nearly finds Ibrahimovic.
90+2 minWhat a block from Zouma! Cavani unleashed a powerful low effort that look destined for the bottom corner, but Zouma stood firm.
90+4 minGOAL! Saint-Etienne 2-2 Paris Saint-Germain (Blaise Matuidi)
90+4 minOn second inspection it may have been Matuidi's goal, but PSG are level! Dramatic scenes here, but Blaise Matuidi, against his former club, puts a cross into the area which bounces in front of Ruffier in a crowd of bodies and goes all the way through and into the back of the net.
90+5 minFULL TIME: Saint-Etienne 2-2 Paris Saint-Germain
9.59pmWow, time to catch your breath. What a finish at the Stade Geoffroy-Guichard, as Blaise Matuidi maintains PSG's unbeaten run in the dying moments.
10pmSaint-Etienne raced to a 2-0 lead with goals from Benjamin Corgnet and Romain Hamouma. However, Fabien Lemoine was then sent off before Edinson Cavani and Matuidi struck.
10pmPSG move back to the top of Ligue 1 with a marginally better goal difference than AS Monaco. Saint-Etienne up to seventh from ninth.
10.03pmBefore I go, let's take a look at the stats.