Indiscipline cost Mikel Arteta's young crop yet again on the South Coast, where William Saliba received the first red card of his career for a last-man foul in the first half - the third sending-off of the Gunners' embryonic campaign.
Arsenal had held out for draws against Brighton & Hove Albion and Manchester City earlier in the season when going down to 10 men, but Andoni Iraola would get one over his former youth teammate Arteta, as Ryan Christie finished off a sublime corner routine before Justin Kluivert's penalty made sure of the result.
As well as being without influential skipper Martin Odegaard, Arsenal lost the equally fundamental Bukayo Saka to the hamstring injury he suffered on England duty, and the pair's absences were well and truly felt in the first half.
Try as Raheem Sterling might, the Chelsea loanee just could not replicate Saka's unrivalled playmaking ability from the right flank, as Arsenal struggled to pick the Bournemouth lock in a forgettable first 25 minutes.
Sterling was then brought off prematurely in response to Arsenal's third red card of the season, as Saliba felt that he had no choice but to make a last-man challenge on Evanilson following an atrocious pass from Leandro Trossard; Rob Jones brought out the yellow card at first before upgrading his punishment.
Arteta's side are well-versed to playing with 10 men by this point, but there would be no consolation point for the Gunners on this occasion, as Christie finished off a wonderful corner play that Arsenal set-piece guru Nicolas Jover would have been proud to mastermind.
Soon it was Jakub Kiwior's turn to play a shocking backpass, which led to David Raya bringing down Evanilson and Kluivert doing the business from the spot, as Arteta experienced one of his most humbling evenings as Arsenal manager in 2024.
Moreover, Arsenal's failure means that the Gunners miss the chance to go top of the Premier League table - they remain third for now - while the Cherries creep into the top half and sit pretty in 10th place.
BOURNEMOUTH VS. ARSENAL HIGHLIGHTS
William Saliba red card vs. Bournemouth (27th min, Bournemouth 0-0 Arsenal)
Just like against Brighton & Hove Albion, just like against Manchester City, Arsenal go down to 10 men once again, as Saliba takes the walk of shame for the first time in his career.
Trossard plays an inexplicable lofted pass back into his own half, which Evanilson is about to race onto before being tugged back by a panicking Saliba.
The incident occurred close to the centre circle, and Ben White may have been covering on the other side, but Jones upgrades his initial yellow card to a red following a check of the monitor.
Ryan Christie goal vs, Arsenal (70th min, Bournemouth 1-0 Arsenal)
The set-piece kings are beaten at their own game!
Bournemouth had not made the full use of their man advantage until now, as a low corner is deftly flicked on by Kluivert to fellow substitute Christie, who directs a sumptuous first-time curler into the top corner.
A dead-ball routine that we would normally expect from Nicolas Jover's Arsenal, but it is the Cherries who finally pick the 10-man lock!
Justin Kluivert goal vs. Arsenal (79th min, Bournemouth 2-0 Arsenal)
It has been a day of backpass calamities for Arsenal, as Kiwior sells Raya incredibly short and sets Evanilson through on goal with the Spaniard, who is already in no man's land and clips the Brazilian as he tries to go around him.
Jones points to the spot straight away, and Raya cannot repeat his heroics from the Champions League draw with Atalanta BC; Kluivert goes from provider to goalscorer by coolly sending him the wrong way.
MAN OF THE MATCH - JUSTIN KLUIVERT
Dropped from the starting lineup after a poor 45 minutes in Bournemouth's loss to Leicester City before the international break, Kluivert changed the game for the hosts when he was introduced in the second period.
The Dutchman played the final, exquisite pass for Christie's opener before clinically sending Raya the wrong way from the penalty spot, and a return to the starting XI surely now beckons.
BOURNEMOUTH VS. ARSENAL MATCH STATS
Possession: Bournemouth 48%-52% Arsenal
Shots: Bournemouth 13-6 Arsenal
Shots on target: Bournemouth 4-1 Arsenal
Corners: Bournemouth 12-11 Arsenal
Fouls: Bournemouth 7-4 Arsenal
BEST STATS
WHAT NEXT?
Arteta's troops have just two full days to rest up before they go again, hosting Shakhtar Donetsk in the Champions League on Tuesday evening, which precedes a heavyweight Premier League battle with Liverpool at the Emirates on October 27 - Saliba's suspension for that game will be a monumental blow.
In contrast, Bournemouth have no midweek matches pencilled into the diary and have a full week to recuperate before they travel to Aston Villa next Saturday afternoon.