Match ends, Bournemouth 2, Arsenal 1.
Manager Arsene Wenger said he would review Arsenal's defeat at Bournemouth in a "harsh way" as goals by Callum Wilson and Jordon Ibe dented the Gunners' pursuit of a top-four place.
Wenger's men are now without a win in five games in all competitions, and five points adrift of fourth place in the Premier League, after Bournemouth came from behind to extend their unbeaten run to four games and move further away from the bottom three.
Defender Hector Bellerin had given the visitors - playing without forward Alexis Sanchez - the lead when he latched on to a defence-splitting Alex Iwobi pass to squeeze the ball past Asmir Begovic.
But Wilson took advantage of Petr Cech's indecision as he got to Ryan Fraser's low cross before the Arsenal keeper and poked it past him.
The 25-year-old then turned provider, bringing down Lewis Cook's cross for Ibe to rifle home.
"We were 1-0 up and suddenly we lost two goals and we don't know where they came from," said Wenger.
"It is very frustrating. Overall we have to look at it in a very objective and harsh way - we made mistakes we should not have made.
"The team that fights against relegation will fight and you cannot afford any concentration mistake.
"One-all was not good enough for us. We had to win the game. I think if you look again at the second goal - we made many mistakes and that is what we paid for."
Eddie Howe's side savoured a first ever Premier League victory over Arsenal, at the sixth attempt, the victory moving them up to 13th place and four points away from danger.
But for Wenger, who was completing his three-game touchline ban for verbally abusing an official, it was further disappointment as speculation mounts that Sanchez's departure is imminent.
A strong first-half Gunners performance, in which 20-year-old Ainsley Maitland-Niles rattled the crossbar, was undone in less than five calamitous second-half minutes.
Wilshere runs midfield but Gunners attack blunted
A Sanchez header triggered Arsenal's fightback in last season's 3-3 draw at the Vitality Stadium, but without him they looked to a 26-year-old 'veteran' for inspiration.
Wenger named his youngest starting line-up in the Premier League since November 2012, and asked Jack Wilshere, one of his senior outfield players for the afternoon, to lead the fight at the club where he spent last season on loan.
For 45 minutes it looked as though Wilshere would be the difference as he ran the midfield. In total he played more passes (74) and had more touches (98) than any other player.
But, for all his commanding presence, and the delicate probing of Iwobi on the right of midfield, it was in attack that Arsenal fell down, managing only three shots on target.
Alexandre Lacazette led the line, contributing to two good goalscoring opportunities when Maitland-Niles hit the bar and Begovic saved from Danny Welbeck, but the £46.5m striker did not manage a single shot himself.
Welbeck behind him could contribute only the effort that Begovic smothered.
Wenger, who is being linked with Bordeaux's Brazilian forward Malcom, will know he must replace Sanchez this month once his departure is confirmed.
Howe's men show their mettle
Sometimes considered a disciple of possession football who only knows one way to play, Cherries boss Eddie Howe continues to suggest there is more subtlety to him.
By selecting a back three and two wing-backs, with captain Simon Francis returning in the middle of the defence, Howe gave his team a robust shape and largely nullified the visitors.
Former Chelsea player Nathan Ake continues to impress, with four tackles and eight clearances, more than any other defender, and Francis weighed in with six clearances.
Francis - for whom attacker Benik Afobe made way - had a big influence, winning 70% of his duels and more headers than anyone.
But a more defensive shape than usual, and 18% less possession overall than the visitors, did not stymie the Cherries as an attacking unit.
In the first half Ryan Fraser's goalbound shot was blocked by Calum Chambers, and the hosts were denied a possible penalty when referee Kevin Friend did not punish an apparent handball from Iwobi as he defended a corner.
Man of the match - Callum Wilson (Bournemouth)
'We paid for our many mistakes' - what they said
Bournemouth boss Eddie Howe, speaking to BBC Sport: "A huge win for us. Every win in the Premier League is important. It was a tight game, not a lot in it, but we showed the spirit and desire to come back from a losing position.
"I am delighted with the attitude of the players. Our fitness levels were very good - statistically we are one of the fitter teams in the division.
"If you can get two or three wins your whole outlook can change, then if you get two or three defeats it all changes. We have just tried to be very stable. That was a famous win for the club."
Cherries get over their 'big six' jinx - the stats
- Bournemouth have recorded their first win against a side from the 'big six' in the Premier League since December 2016 (4-3 v Liverpool), ending a run of 14 winless games (D3 L11), including nine successive losses.
- Arsenal have picked up just 13 points after 12 Premier League away games (W3 D4 L5) - their worst record at this stage of a season since 2005-06 (12 points from 12 games).
- The Cherries have won their first ever game against Arsenal in all competitions (D1 L5).
- Arsenal have lost the past three Premier League games that Sanchez has not played any part in - 1-0 at Stoke, 2-1 at Watford and against Bournemouth.
- At average age of 25 years and 56 days old, this was Wenger's youngest Arsenal starting line-up in the Premier League since November 2012 v Aston Villa (25y 11d).
- The Frenchman also named five English starters in a Premier League game for just the third time since 2003.
- Thirteen English players started the match, the most in a Premier League game involving Arsenal since January 2002 (Leeds v Arsenal, 14).
- Wilson has scored three goals in three Premier League games against the Gunners, and also recorded his first ever Premier League assist when setting up Ibe for the winning goal.
Bournemouth travel to Wigan for their FA Cup third-round replay on Wednesday (19:45 GMT), while Arsenal host Crystal Palace at the Emirates on Saturday 20 January (15:00 GMT).
- 2FrancisBooked at 31mins
- 3S Cook
- 15A Smith
- 16L Cook
- 4GoslingBooked at 21mins
- 11DanielsSubstituted forMoussetat 63'minutes
- 33IbeSubstituted forPughat 86'minutes
- 13WilsonSubstituted forAfobeat 90+1'minutes
- 21ChambersSubstituted forRamseyat 74'minutes
- 10WilshereBooked at 71mins
- 29XhakaBooked at 56mins
- 17IwobiSubstituted forWalcottat 76'minutes
- Kevin Friend
- Shots on Target
Second Half ends, Bournemouth 2, Arsenal 1.
Offside, Arsenal. Alexandre Lacazette tries a through ball, but Héctor Bellerín is caught offside.
Corner, Bournemouth. Conceded by Granit Xhaka.
Substitution, Bournemouth. Benik Afobe replaces Callum Wilson.
Attempt missed. Granit Xhaka (Arsenal) left footed shot from outside the box misses to the left.
Substitution, Bournemouth. Marc Pugh replaces Jordon Ibe.
Offside, Arsenal. Alexandre Lacazette tries a through ball, but Theo Walcott is caught offside.
Hand ball by Callum Wilson (Bournemouth).
Attempt missed. Jordon Ibe (Bournemouth) right footed shot from outside the box is close, but misses to the left. Assisted by Adam Smith.
Offside, Arsenal. Shkodran Mustafi tries a through ball, but Theo Walcott is caught offside.
Attempt missed. Jack Wilshere (Arsenal) left footed shot from outside the box misses to the right. Assisted by Granit Xhaka.
Foul by Aaron Ramsey (Arsenal).
Lewis Cook (Bournemouth) wins a free kick in the defensive half.
Substitution, Arsenal. Theo Walcott replaces Alex Iwobi.
Attempt missed. Ryan Fraser (Bournemouth) right footed shot from outside the box is too high following a set piece situation.
Hand ball by Héctor Bellerín (Arsenal).
Goal! Bournemouth 2, Arsenal 1. Jordon Ibe (Bournemouth) right footed shot from the centre of the box to the centre of the goal. Assisted by Callum Wilson.
Substitution, Arsenal. Aaron Ramsey replaces Calum Chambers.
Attempt missed. Granit Xhaka (Arsenal) left footed shot from outside the box misses to the right. Assisted by Jack Wilshere.