Arsenal 3 West Brom 1 - Report
Albion's relegation to the Championship with confirmed after they were beaten by Arsenal.
The Baggies headed to The Emirates knowing they had to win to avoid their drop into English football's second-tier becoming official.
But a stunning Matheus Pereira goal wasn't enough with strikes from Emile Smith Rowe, Nicolas Pepe and Willian seeing the Gunners to a 3-1 win.
That scoreline massively flattered the hosts, though, with the Baggies putting in a real battling display in the capital.
Sam Allardyce's side dominated the opening 20 minutes but they couldn't make that good play count with the hosts then going in at the break with a two-goal cushion thanks to a quick-fire double from Smith Rowe and Pepe.
Pereira gave the Baggies hope of a fightback when he scored a magical goal after the interval.
The Brazillian picked up the ball in his own half and carried it 50-yards before firing past Bernd Leno.
Allardyce's men then pushed for an equaliser with Darnell Furlong going close.
But in the 90th minute, Willian sealed Albion's fate when he curled in a free-kick from 25-yards.
Report
Allardyce made two changes from the team that played out a draw with Wolves when naming his starting line-up.
With loanee Ainsley Maitland-Niles unable to play against his parent club, Matt Phillips came back into the side and started in central midfield alongside Okay Yokuslu and Conor Gallagher.
In what was a 4-3-3 system, Callum Robinson also earned a recall on the right wing with Matheus Pereira on the left and Mbaye Diagne the central striker.
On the bench, youngsters Caleb Taylor and Taylor Gardner-Hickman were named in an Albion squad for the first time.
Arsenal, fresh from being dumped out of the Europa League by Unai Emery's Villarreal on Thursday, lined up in a 4-2-3-1 formation.
It saw Gabriel Martinelli start as a lone centre-forward with Smith Rowe in the number 10 role.
Willian was on the left flank with Pepe was on the right.
The game kicked off amidst a backdrop of Arsenal fans protesting outside the stadium - with those supporters unhappy with Stan Kroenke's ownership of the club and the decision to sign the Gunners up to the disastrous European Super League.
Whether Arsenal were suffering with a hangover from their Europa League exit or Albion simply had more hunger - it was the Baggies who charged out the blocks and dominated the opening 20 minutes.
Both Pereira and Robinson had powerful shots inside the area blocked by some last-ditch defending.
A moment of brilliance from Pereira then saw the Brazilian let-fly with an outrageous strike from 25-yards that sailed just millimetres past the post.
The Baggies were looking compact at the back but they were also moving the ball really well when going forward.
And they threatened once again when Pereira fizzed a delicious ball across the six-yard box.
That was met by a stretching Diagne. But while the striker made contact with the ball, he couldn't get enough on it to turn it goalwards.
Arsenal's only threat had been down the left side with Bukayo Saka who was playing at left-back but was operating more as a left winger.
Twice the England man hit the byline and sent in dangerous crosses which nobody got on the end of.
But as the half reached the midway point, the Gunners started to enjoy more control.
And it was Saka who created their opening goal with the 19-year-old again hitting the byline and sending in a cross which - this time -was turned in by Smith Rowe.
That goal completely changed the mood in the Arsenal camp with Arteta's men suddenly a lot more relaxed.
And they doubled their lead just six minutes later when Pepe darted into the box before cutting inside and curling a brilliant strike into the far corner.
That goal effectively confirmed Albion's relegation.
And it showed on the pitch with the Baggies looking visibly deflated while Arsenal zipped the ball about as they coasted to half-time.
It was Arsenal who created the first chance following the re-start with Pepe collecting the ball in the box before hitting a low drive which Johnstone got down well to beat away.
Allardyce made his first change in the 56th minute with Hal Robson-Kanu replacing Diagne up front.
Alexandre Lacazette then replaced Martinelli for the hosts.
Albion were now operating with Phillips on the right in a bid to give Darnell Furlong - who had been horribly exposed in the first half - more protection up against Willian and Saka.
But the England man continued to cause problems with Saka sending in another low cross that Smith Rowe really should have tapped home.
In the 67th minute, though, Albion gave themselves some hope when Pereira scored a truly exceptional goal.
The Brazilian picked up the ball in his own half and rode a number of challenges to carry it the best part of 50-yards.
And then having got himself to the edge of the area, he brilliantly found the bottom corner with an effort Bernd Leno couldn't get near.
In the celebrations, Allardyce introduced Grady Diangana for Robinson.
And Albion should have got themselves level just moments later when Phillips whipped in a wonderful cross.
That was met by Furlong but from six yards the defender sent a glancing header wide when he really should have scored.
Albion huffed and puffed from that point, with Allardyce's men pushing Arsenal back in a bid to find an equaliser that would, at least, prevent their relegation.
But in the 90th minute, the Gunners sealed their fate when Willian scored a stunning free-kick from the edge of the box.
Teams
Arsenal (4-2-3-1): Leno, Chambers, Holding, Gabriel, Saka, Elneny, Ceballos (Partey 76), Pepe, Smith Rowe (Tierney 63), Willian, Martinelli (Lacazette 60).
Subs not used: Runarsson, Bellerin, Odegaard, Aubameyang, Soares, Nketiah.
Albion (4-3-3): Johnstone, Furlong, Ajayi, Bartley, Townsend, Yokuslu, Phillips, Gallagher, Pereira, Robinson (Diangana 68), Diagne (Robson-Kanu 56).
Subs not used: Button, Peltier, O'Shea, Taylor, Livermore, Gardner-Hickman, Grant.