Monreal opened the scoring for the Gunners in the 16th minute, before Iwobi netted 11 minutes into the second half to see the home side move into fifth place in the table.
Brighton impressed on Sunday afternoon and struck the post through Solly March, but the Seagulls did not do enough after the restart to try to claim a result.
Find out how all of the action unfolded at the Emirates Stadium courtesy of Sports Mole's minute-by-minute updates below.
11.01amHello and welcome to Sports Mole's live coverage of the match in the Premier League between Arsenal and Brighton & Hove Albion. After Chelsea slipped up yesterday, it has allowed Arsenal the chance to try to move level on points with their London rivals. How do they line up today? Let's find out.
11.06amRight then, let's start with Arsenal, who have lined up slightly differently to what I was expecting.
Let's start at the back and tell you that Rob Holding is lining up on the right-side of a three-man defence which sees Shkodran Mustafi take his place in the centre. That's because Laurent Koscielny misses out completely, and Per Mertesacker is only selected on the bench.
11.08amSead Kolasinac was another option on the left side of defence but he will start at left wing-back, with Hector Bellerin beginning the game on the opposite flank. Aaron Ramsey and Granit Xhaka get the nod in the middle of the park, meaning that Jack Wilshere does not get a second start in the space of three days. Maybe a wise decision...
11.10amFurther forward, both Alexis Sanchez and Alexandre Lacazette return as expected, but Alex Iwobi comes back into the squad after missing out in midweek. The 21-year-old has only featured for 91 minutes of Premier League football this season, but he finally gets another chance to impress.
11.12amOf those we haven't mentioned, Theo Walcott and Olivier Giroud both feature among the replacements, despite netting against BATE Borisov in midweek, while the other two outfield places are taken up by Mohamed Elneny and Ainsley Maitland-Niles, who will hope to make just his second league outing of the season in the second half.
11.14amLet's get onto the Brighton team, because Chris Hughton has made a total of three alterations to the team who beat Newcastle United last weekend. We will start in attack, because Tomer Hemed is missing through suspension. Isaiah Brown - the Chelsea loanee - is the player to take his place. The versatile attacker has not featured in the Premier League since getting injured on the opening day of the season.
11.16amAnother change comes on the flank, with Jose Izquierdo, who is making his first Premier League start for the Seagulls. Somewhat surprisingly, he replaces Anthony Knockaert, whose work-rate may have proven valuable this afternoon.
11.18amHughton has also decided to tinker in defence, too, with Gaetan Bong making his first Premier League appearance of the season, with Markus Suttner dropping down to the bench. Again, that's an interesting change for the trip to the Emirates Stadium. Maybe Hughton is just taking the chance to give some of the players more time on the pitch?
11.20amWenger has been speaking about Brighton's qualities ahead of this match, saying: "I think it will be difficult to break them down because they are very well organised, they are very disciplined as well. Their team keeps the ball well and from what I've seen they have a good technical quality, they try to play everywhere and it is a different challenge for us."
We will have to see about that. Arsenal are rather good when playing newly-promoted sides...
11.22amArsenal are unbeaten in their last 31 matches in the Premier League against newly-promoted sides, which is a phenomenal record. Their last defeat came all the way back in 2012, when they were defeated by Queens Park Rangers.
11.24amThere's also a link between the last newly-promoted side to win a game at the Emirates Stadium because on that occasion in 2010, it was Chris Hughton who guided his Newcastle United to victory thanks to a header from Andy Carroll.
11.26amLet's get back to speaking about Arsenal in a more positive light because they can equal a record this afternoon. The Gunners have registered eight straight victories in the Premier League at the Emirates Stadium, and that leaves the club just one short of their all-time record at their North London home.
11.27amArsenal are also looking to continue their run of clean sheets in the Premier League. The next shutout looked a mile off when they lost 4-0 at Liverpool, but since then, they have prevented Bournemouth, Chelsea and West Bromwich Albion all from scoring. It means that they are just shy of going 300 minutes without conceding. Not bad for a team who are said to be weak in their defensive third...
11.29amThat said, it is worth pointing out how poor Arsenal looked at the back when they faced BATE Borisov in the Europa League on Thursday night. Wenger did rotate his troops, but both Holding and Mustafi feature today. Maybe a cause for concern for the home supporters...?
11.31amHowever, let's get back to talking about records, because there are several on the line.
Wenger is looking to claim a win over a 45th different Premier League manager. Given Hughton's experience, how he hasn't got the better of Hughton in his career, I don't know. Anyway, win this afternoon and Wenger will surpass Sir Alex Ferguson's long-standing record.
11.33amLacazette is also looking to move into the record books. The summer signing has scored in his first three home league fixtures and if he nets in a fourth, it will equal the record of Jackie Henderson who achieved the feat in 1958.
11.35amIt's about time we bring Brighton more into the equation, but we aren't exactly going to fill their supporters with optimism. Sorry about that.
Brighton have made a solid start to the top flight, but today's visitors have only won one of their last 32 matches on the road at the first tier of English football.
11.37amThey have also failed to win away in any competition this season. They've only played Leicester City, Watford and Bournemouth (twice) on the road but they remain without a win, have registered just one point against a team with 10 men and have netted one goal. It's hardly the best preparation for facing Arsenal in North London...
11.39amThey are also without a player in Hemed who has netted 40% of their goals since winning promotion to the Premier League. They still have Pascal Gross - who has been a revelation since making the switch to the Amex Stadium - but Hemed may be a big miss, although the pace of Brown may work against a three-man Arsenal defence missing Koscielny.
11.41amHEAD TO HEAD! Today's match represents just the 16th time in which these two teams have met in a competitive fixture. That probably doesn't come as a surprise to you! It also won't shock you that Arsenal have won all but four of the previous matches, with Brighton gaining just two victories.
11.43amToday's match will also be the first league contest since 1983. Back then, in the old Division One, Arsenal ran out 3-1 victors at Highbury, with Raphael Meade and Graham Rix both getting on the scoresheet. Thirty-four years is a long time for teams not to have played each other in a league match, but the clubs are more familiar with each other than you may think.
11.44amSince 1983, there have been three encounters in the FA Cup and although Brighton have scored in each of them, Arsenal have always prevailed by a one-goal margin. Two of those three matches have come in 2013 and 2015 respectively, with both fixtures turning out to be five-goal thrillers.
11.46amIn 2013, Brighton twice came from behind to head into the closing stages on level terms before they were ultimately outdone by a late goal from Theo Walcott. That came in the fourth round of the world's greatest cup competition. To read back on that game, click here.
11.49amIt was at the same stage where the teams met two years later, with three goals in the opening hour proving enough for the Premier League side to get the job done. There was even a rare appearance and goal for Tomas Rosicky! To refresh your memory on the ins and outs of that encounter, click here.
11.51amPREDICTION! It's prediction time and you can probably guess who we are going to take a punt on. It has to be Arsenal, who certainly seem to be clicking into gear before the next international break. Wenger thinks that his side will struggle to break Brighton down, but we have to disagree. Arsenal to claim a 4-1 victory, and the Gunners, Wenger and Lacazette all to enter the record books.
11.53amIt's a bumper day in the Premier League with this fixture only acting as the first of three matches. We will also have full coverage of Everton's home clash with Burnley, and Liverpool's trip to St James' Park to face Newcastle United. We hope that you can stick around for both of those games.
11.55amIt's time for the two teams to make their way out at the Emirates Stadium. The bleary-eyed faces seem to be at a minimum but let's hope the game keeps everyone awake after an assumed late night.
11.58amA reminder on the team news. Wenger has gone back to his first XI after the trip to BATE Borisov, but there is no Koscielny at the back. Hughton has made three changes from last week's win over Newcastle, with Gaetan Bong, Isaiah Brown and Jose Izquierdo coming into the team.
2 minWOODWORK! Arsenal strike the post without Brighton touching the ball! Lacazette lets fly with a missile of a shot from distance but the ball cannons off the woodwork and Sanchez can't net the rebound.
4 minArsenal already look in the mood. This could be a long afternoon for Brighton if Arsenal score early. It's more possession for the Gunners but no more chances to speak of.
5 minCHANCE! Very impressive response from Brighton. After winning a free kick on the touchline, the ball is curled into the box and Brown glances a header wide of the far post. If a player was waiting at the back post, it's 1-0.
7 minThere's just a wall of yellow shirts in and around the penalty area. Brighton's plan is obviously to defend in numbers and use the pace of Gross, Izquierdo and Brown to break forward.
7 minSHOT! A period of sustained possession doesn't lead to Arsenal making any ground, so Sanchez decides to shoot from more than 30 yards. It's a half-decent strike, but Ryan has no trouble making the save.
10 minWe've had a quiet few minutes purely because of players having issues with their boots. I'm sure it has nothing to do with any time-wasting from Brighton at this early stage. Both sides will be pleased with the start they have made.
12 minThere's an extended lull in the action in North London. Arsenal are content to spray the ball about, trying to tempt Brighton out of defence. Brighton aren't having it.
13 minCHANCE! Much better from Arsenal. Much quicker and direct too. Sanchez slides a ball through to Iwobi, who should probably find the far corner from 14 yards but his effort is too close to Ryan.
15 minArsenal are doing a good job of pressing Brighton each time the visitors have the ball, so the visitors are barely getting past the halfway line. It's not exactly one-way traffic but the home side are in control.
16 minGOAL! Arsenal 1-0 Brighton & Hove Albion (Nacho Monreal)
16 minIf we had predicted that Monreal would open the scoring with a right-foot shot, you would have laughed at us, but that is exactly what has happened.
From a free kick, Brighton clear off the line and make blocks aplenty, but the ball eventually lands at the feet of Monreal, who scuffs the ball into what is effectively an empty net from 12 yards out.
18 minBrighton protested that the ball had already gone out from the initial free kick, but it hadn't. Gross has received a booking for his complaints.
20 minIn fairness to Brighton, they have attempted to hit straight back. A cross from the right needed to be diverted behind by a defender, before the corner itself created problems for Cech. Brighton are still in this, both mentally and by the scoreline.
22 minArsenal have conceded a number of sloppy fouls in this match. The guilty party on this occasion is Kolasinac, who gives Brighton the chance to get the ball into the box from the side of the penalty area.
23 minWOODWORK! What a hit from March! A clever set-piece routine gives March the chance to shoot from 25 yards and like Lacazette in the opening minute and a bit, his driven strike cannoned off the post. Dunk could and should have scored the rebound but he directed the ball wide from about 14 yards out.
26 minBrighton are matching Arsenal right now. It's as if complacency has set in with Arsenal and Brighton are only increasingly motivated having conceded a goal. The visitors are the better team now.
27 minAnother cross into the box, more problems for Arsenal. The referee has just awarded a corner against them when the ball wasn't out as well. Nothing came from it this time, but Brighton really fancy this.
29 minCHANCE! Iwobi has done well on his return to the team but the 21-year-old should do a lot better here. Slowly but surely, the Nigerian got closer towards goal but he scuffed his eventual effort straight at Ryan.
32 minWe have just had thirty seconds with a standoff between the referee and Xhaka. There was a dispute over where the ball should be placed for a free kick. Guess who won?
Xhaka sent his shot into the wall. To be fair, the wall appeared to be about five yards away.
34 minCHANCE! A slip in the Brighton defence leads to a two-on-one situation which is led by Lacazette. He rightly goes himself but he scuffs his curler straight at Ryan. I've said that a few times this afternoon.
36 minBrighton are starting to unravel at the back. Passes are going astray and Arsenal are forcing the visitors into mistakes. It's an important 10 minutes in this game. Brighton cannot afford to concede a second.
38 minWhen Arsenal have the ball, there is not one player left in their own half. Holding and Monreal are practically defensive wingers. The Gunners recognise that the second goal is there for the taking.
39 minBOOKING! Duffy eases the pressure by hacking down Sanchez. It's very late and the Republic of Ireland defender deserves his booking.
42 minCHANCE! Brighton fail to make the most of numerous chances around the penalty area and it leads to a stunning break from Arsenal. Bellerin plays in Xhaka, who pulls the ball back for Ramsey who should score from eight yards but Ryan sticks out a leg to make a brilliant save.
44 minThis has been some half of football. Naturally, the fear was that Brighton would get outclassed but this has materialised into a 50-50 contest. Hughton will be so encouraged by this performance.
45 minCHANCE! Another opportunity for Brighton, Izquierdo does well against Mustafi on the right-hand side of the penalty area before teeing up Propper, but the Dutchman curls the ball over the bar when aiming for the far corner.
45+1 minHALF TIME: Arsenal 1-0 Brighton & Hove Albion
12.47pmThe half-time whistle goes at the Emirates Stadium and we remain at 1-0 to the Arsenal. I have no idea how. It has been a terrific game and while Arsenal should have three goals to their name, Brighton can count themselves unfortunate not to be on level terms.
12.50pmArsenal lead thanks to Monreal's goal, with the Spaniard eventually converting after a scramble inside the penalty area. Brighton were protesting that the ball had gone out earlier in the passage of play, but the ball was on the line so they cannot feel hard done by.
12.53pmThe home side have also had chances through Iwobi and Ramsey. Iwobi's first chance and Ramsey's eight-yard attempt should have definitely led to goals. It's only a combination of poor finishing and a miracle save from Ryan that they didn't.
12.57pmBrighton have created numerous threatening moments, but the one which sticks out is March's effort which struck the post. It came from an excellent free-kick routine before the midfielder hit the woodwork from 25 yards. Cech was beaten in the Arsenal goal.
1.01pmThe two teams have made their way back out at the Emirates. It doesn't appear like any changes have been made by either side.
46 minBrighton get us back underway in the second half.
47 minIt's been a low-key start but maybe that was inevitable after the energy put into the opening 45 minutes. Sanchez has played one poor pass in the final third but that's about it.
49 minLacazette is about to put Arsenal two goals to the good from 10 yards, until Duffy makes a superb block to deny the Frenchman. The striker has looked dangerous every time he has received the ball today.
52 minSHOT! Ramsey wastes a volley on the edge of the area, but this half still hasn't sparked into life. Arsenal are in control but they cannot afford to be complacent. We saw what could happen in the first half.
54 minCHANCE! Sanchez plays the deftest of crosses towards Ramsey but Duffy does well to get ahead of the midfielder, although Ryan has to be alert to prevent the own goal!
55 minSHOT! This is ambitious from Dunk but it nearly leads to a goal. The centre-back strides forward before firing a shot on goal, with Cech doing well to claim low to his right.
56 minGOAL! Arsenal 2-0 Brighton & Hove Albion (Alex Iwobi)
56 minArsenal finally have their second goal. A couple of sharp passes find Sanchez inside the penalty area, who then back-heels the ball into the path of Iwobi who takes his time before finding the top corner from 14 yards.
59 minThe home side are relentless in search of a third goal here. Brighton are sitting deeper and deeper which probably isn't a smart thing to do. Arsenal have been good today, against threatening opponents.
61 minBrighton have attempted to put together a couple of moves down the right flank but they have broken down before the ball found its way into the box. It might be time for Hughton to make a change.
61 minSAVE! I tell you something - Ryan has been sensational in this game. Sanchez has all the time in the world to try to score, but the goalkeeper sticks out a hand to tip the shot wide.
62 minCHANCE! Brighton now clear off the line! Xhaka's corner found the head of Kolasinac, who beat Ryan but not the player on the line. It's relentless from Arsenal.
65 minWith the visitors now having to throw more caution to the wind, the space is opening up in the final third for Arsenal but they almost have too many options to select from! Sanchez has just tried an old-fashioned toe-punt but he gets it all wrong.
67 minI'm not sure how Lacazette hasn't scored this afternoon. Again, he looks in prime position to find the bottom corner but Dunk gets back to put the block in. Duffy and Dunk have been excellent.
69 minI'm surprised that neither side have made a change yet. I suppose it is showing the value in Wenger making mass changes for the trip to Belarus. However, I thought that Hughton may have acted by now. The Brighton boss has options.
71 minSUBSTITUTIONS! Wenger acts first, with Lacazette and Iwobi being replaced by Theo Walcott and Olivier Giroud.
72 minSUBSTITUTION! There's a switch for Brighton too, with Schletto replacing March. This is the Italian's first appearance in the Premier League.
74 minDunk has just played a dream ball to Schletto, who got down the right flank, but his eventual cross was well cut out by Mustafi, with Brown lurking.
76 minSHOT! Sanchez gets put on his backside on the edge of the area and it's a free kick to the Gunners. The Chilean steps up to take it, but curls the ball well off target.
77 minSUBSTITUTIONS! Hughton has made his final two alterations, with Knockaert and Murray replacing Izquierdo and Brown.
80 minJust the 10 minutes to go at the Emirates. There's not a whole lot happening, although Brighton certainly haven't thrown in the towel. They have given a good account of themselves this afternoon.
82 minTo their credit, Brighton have had a bit more joy in the last few minutes but as it stands, Arsenal are in control of matters at the back.
83 minSUBSTITUTION! A third and final change for Arsenal sees Elneny replace Xhaka.
84 minCHANCE! Brighton come within inches of an equaliser. Knockaert's cross finds the run of Murray, who beats Mustafi in the air and heads the ball into the side-netting.
86 minKnockaert has done more in 15 minutes that Izquierdo did in 70. It was a surprise omission and it is proving to be the wrong choice. Arsenal are having to do a lot of defending now.
87 minI tell you something. Brighton have a sniff here. Mustafi has just glanced the ball a couple of yards wide of his own goal to deal with a cross. The Gunners are all over the place at the back.
89 minThat spell of pressure may have come to an end. Brighton are still having all of the ball but Arsenal have pushed out to ease the pressure on the backline.
90 minThere will be three minutes of added-on time.
90+2 minSHOT! Another brilliant chance for Brighton. Propper has time to send a first-time effort on goal from 20 yards but he curls the ball inches wide of Cech's post.
90+3 minFULL TIME: Arsenal 2-0 Brighton & Hove Albion
1.55pmThe full-time whistle goes at the Emirates Stadium and Arsenal have held on to register a 2-0 win over Brighton. Goals from Monreal and Iwobi proved to be the difference as the Gunners moved into fifth place in the table. Brighton remain in 14th place after giving a good account of themselves in North London.
1.57pmThat will be all from Sports Mole for this game. Thank you for joining us this afternoon and we hope that you can stick around for the other two Premier League games this afternoon.
If you want to read our match report from this game, click here. Goodbye for now.