Jan Bednarek's fourth goal of the season earned Southampton their first victory since February
Arsenal missed the chance to move level on points with fourth-placed Tottenham as Southampton won at St Mary's to inflict a third successive defeat on Mikel Arteta's team.
Jan Bednarek scored the game's only goal late in the first half after the Gunners had failed to adequately deal with a Saints corner.
Bukayo Saka was denied from point-blank range by Southampton goalkeeper Fraser Forster with the score still goalless, but further clear-cut openings proved hard to come by for the visitors until the closing stages of the second half.
Emile Smith Rowe forced another fine save out of Forster after latching on to Yan Valery's attempted clearance, before Martin Odegaard dragged a left-footed shot wide of the near post after cutting in from the right.
Forster produced yet another impressive stop to deny Granit Xhaka late on as Arsenal desperately piled forward in search of an equaliser.
The Gunners remain three points behind fourth-placed Tottenham - who were beaten at home by Brighton earlier on Saturday - although they do still have a game in hand on their north London rivals.
Southampton, meanwhile, climb to 12th after claiming their first league win since February.
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Magnificent Forster keeps Gunners at bay
Following lacklustre displays at Crystal Palace and at home to Brighton last weekend, Gunners fans may have hoped this trip to St Mary's would prove to be an ideal fixture to reignite their top-four push.
Saints had lost five of their past six matches in all competitions before Saturday and conceded 19 goals in the process - including a 6-0 capitulation at home to Chelsea in their last match. They had also won only one of their past 12 meetings with Arsenal in the Premier League.
The hosts had Forster to thank for keeping the score goalless in the early stages of the first half, the veteran goalkeeper getting down low to palm Gabriel Martinelli's curling shot past the post before brilliantly tipping Saka's close-range effort over the bar following an error from Valery.
Although the Gunners continued to dominate possession as the half wore on, they lacked the tempo to create further openings against a resolute and defensively organised Southampton. The hosts then punished Arsenal when Bednarek fired home his fourth goal of the season with a minute of the first half remaining.
When Arsenal did manage to penetrate the Saints rearguard late in the second half, they found Forster in inspired form. The 34-year-old did magnificently to parry Smith Rowe's goal-bound effort wide before getting in the way of a low Saka shot.
Forster also managed to get his fingertips to Xhaka's curling strike with the clock ticking towards 90 minutes - although the Switzerland international's effort may have been heading narrowly wide.
Arsenal still have a game in hand on Spurs in fourth but with matches against Chelsea, Manchester United and West Ham coming up in the next fortnight, this will go down as a missed opportunity for Arteta and his players.
Player of the match
ForsterFraser Forster
with an average of 7.48
- SouthamptonSouthamptonSouthamptonArsenalArsenalArsenal
SouthamptonAvgSquad number44Player nameForsterAverage rating
7.48
Squad number21Player nameLivramentoAverage rating
7.37
Squad number8Player nameWard-ProwseAverage rating
7.24
Squad number7Player nameLongAverage rating
7.20
Squad number17Player nameS ArmstrongAverage rating
7.16
Squad number35Player nameBednarekAverage rating
7.07
Squad number2Player nameWalker-PetersAverage rating
7.07
Squad number18Player nameBrojaAverage rating
7.04
Squad number11Player nameRedmondAverage rating
7.04
Squad number24Player nameElyounoussiAverage rating
6.86
Squad number6Player nameOriol RomeuAverage rating
6.84
Squad number15Player namePerraudAverage rating
6.78
Squad number4Player nameLyancoAverage rating
6.63
Squad number43Player nameValeryAverage rating
6.55
ArsenalAvgSquad number7Player nameSakaAverage rating
5.03
Squad number32Player nameRamsdaleAverage rating
4.69
Squad number35Player nameGabriel MartinelliAverage rating
4.65
Squad number8Player nameØdegaardAverage rating
4.57
Squad number4Player nameWhiteAverage rating
4.34
Squad number6Player nameGabriel MagalhãesAverage rating
4.27
Squad number34Player nameXhakaAverage rating
4.17
Squad number23Player nameSambi LokongaAverage rating
4.10
Squad number30Player nameNketiahAverage rating
4.04
Squad number20Player nameNuno TavaresAverage rating
4.02
Squad number17Player nameCédric SoaresAverage rating
3.90
Squad number10Player nameSmith RoweAverage rating
3.64
Squad number19Player namePépéAverage rating
3.16
- Line-upsMatch StatsLive Text
Line-upsSouthampton
Formation 3-4-3
44Forster43Valery4Lyanco35Bednarek2Walker-Peters8Ward-Prowse6Romeu15Perraud17S Armstrong18Broja24Elyounoussi
- 44Forster43Valery4Lyanco35Bednarek2Walker-Peters8Ward-Prowse6Romeu15Perraud17S ArmstrongSubstituted forRedmondat 82'minutes18BrojaBooked at 56minsSubstituted forLongat 74'minutesBooked at 90mins24ElyounoussiSubstituted forLivramentoat 90+2'minutes
Substitutes
- 5Stephens7Long9A Armstrong10Adams11Redmond13Caballero21Livramento22Salisu23Tella
Arsenal
Formation 4-3-3
32Ramsdale17Cédric Soares4White6Gabriel20Tavares8Ødegaard23Sambi Lokonga34Xhaka35Martinelli30Nketiah7Saka
- 32Ramsdale17Cédric SoaresSubstituted forSmith Roweat 60'minutes4WhiteBooked at 90mins6Gabriel20TavaresSubstituted forPépéat 70'minutes8Ødegaard23Sambi Lokonga34Xhaka35Martinelli30Nketiah7Saka
Substitutes
- 1Leno10Smith Rowe16Holding19Pépé25Elneny38Azeez61Ogungbo69Swanson82Hutchinson
Referee:Peter BankesAttendance:31,465Match StatsHome TeamSouthamptonAway TeamArsenalPossessionHome24%Away76%ShotsHome9Away23Shots on TargetHome3Away6CornersHome6Away8FoulsHome6Away6Live TextPost update
Match ends, Southampton 1, Arsenal 0.
90'+6'Full Time
Second Half ends, Southampton 1, Arsenal 0.
90'+5'Post update
Attempt saved. Gabriel Magalhães (Arsenal) header from the centre of the box is saved in the centre of the goal. Assisted by Martin Ødegaard.
90'+5'Booking
Shane Long (Southampton) is shown the yellow card.
90'+5'Post update
Martin Ødegaard (Arsenal) wins a free kick in the attacking half.
90'+5'Post update
Foul by Shane Long (Southampton).
90'+4'Post update
Attempt missed. Gabriel Martinelli (Arsenal) left footed shot from outside the box is high and wide to the left. Assisted by Bukayo Saka.
90'+2'Post update
Attempt saved. James Ward-Prowse (Southampton) right footed shot from long range on the left is saved in the bottom left corner.
90'+2'Substitution
Substitution, Southampton. Valentino Livramento replaces Mohamed Elyounoussi.
90'+1'Booking
Benjamin White (Arsenal) is shown the yellow card for a bad foul.
90'+1'Post update
Foul by Benjamin White (Arsenal).
90'+1'Post update
Mohamed Elyounoussi (Southampton) wins a free kick on the left wing.
89'Post update
Foul by Granit Xhaka (Arsenal).
89'Post update
Shane Long (Southampton) wins a free kick on the right wing.
87'Post update
Attempt blocked. Gabriel Martinelli (Arsenal) right footed shot from the centre of the box is blocked. Assisted by Albert Sambi Lokonga.
85'Post update
Attempt missed. Martin Ødegaard (Arsenal) left footed shot from outside the box is close, but misses the top left corner following a corner.
85'Post update
Corner, Arsenal. Conceded by Fraser Forster.
85'Post update
Attempt saved. Granit Xhaka (Arsenal) left footed shot from outside the box is saved in the bottom right corner. Assisted by Emile Smith Rowe.
85'Post update
Attempt blocked. Granit Xhaka (Arsenal) left footed shot from outside the box is blocked. Assisted by Albert Sambi Lokonga.
83'Post update
Albert Sambi Lokonga (Arsenal) wins a free kick in the defensive half.
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Source: bbc.com