Two Craig Dawson headers and a Hal Robson-Kanu toe-poke heaped more pressure on Arsene Wenger today as the Baggies put to rest any concerns they had downed tools at 40 points.
The right-back nodded in corners in the 12th and 75th minute to bookend a fantastic home performance against the under-fire Gunners.
Robson-Kanu scored his second goal of the season a minute after coming on for Salomon Rondon as the Baggies hit 43 points - the same tally they finished last season with - and with nine games still to play.
Albion started brightly, with a superhuman burst from Allan Nyom past three Arsenal players down the left wing waking everyone up.
James McClean tested Petr Cech with a stinging shot following a typically swift counter-attack so it was arguably deserved when Dawson nodded in the resulting corner after a late near-post run to give the Baggies the lead.
Not that it lasted long. Just three minutes later Sanchez, who was left in acres of space at the back post, was easily picked out, darted inside, and roofed his finish.
Just after the half-hour mark Aaron Ramsey forced Ben Foster into a full-stretch save before Nyom dug out a clearance with Sanchez biting at his ankles, and then a minute later, Darren Fletcher forced Cech into a similar save after Jake Livermore had played him through.
That was the Arsenal keeper's last contribution though, because he was forced off soon after with what looked like a rolled ankle before an enjoyable first half ended even.
Ten minutes after half-time, Tony Pulis brought off the ineffective Salomon Rondon and threw on Hal Robson-Kanu. It proved to be an inspired decision.
Barely a minute later, the Wales international toe-poked a shot past David Ospina after Chadli had lifted the ball over the defence.
James McClean was standing in an offside position but he let the ball go through his legs and the goal was rightly allowed to stand.
Danny Welbeck then crashed a header against the crossbar from a corner, before Robson-Kanu nearly added a second after Shkrodan Mustafi's mistake.
Ospina rushed out to snaffle the shot but then Chadli rounded the keeper and had his shot cleared off the line.
But the Baggies weren't ruing that miss for long, because in the 75th minute Dawson added his second and Albion's third. It was another header from a corner and it put the Baggies in control.
Wenger brought the limping Alexis Sanchez off soon after and the hosts comfortably saw the game out to get back to winning ways at home.
Tony Pulis and Arsene Wenger have always espoused vastly different styles, and they've fallen out over it plenty of times in the past.
These days the rivalry has mellowed, but the differences between the two remain as pronounced as ever. At times, this was a breathless battle between two contrasting teams.
The visitors kept the ball for long periods of time and probed at the Baggies back-line over and over again, while the hosts happily sat back and invited pressure onto themselves before counter-attacking at break-neck speed. Boy, did it work.
The game's natural order was set early on, with Arsenal camped in Albion's half while the home side kept 10 men behind the ball and invited their visitors to break them down.
But the Baggies have been dangerous on the break this season, particularly at home.
It was one of those sweeping moves up the pitch that led to a corner in the 12th minute when Petr Cech palmed James McClean's stinging shot behind following a pin-point pass from Chris Brunt and good hold-up play from Salomon Rondon.
Before the match, Arsene Wenger warned his side about Albion's threat from set-plays, no Premier League team has scored more from dead balls this season.
But it either fell on deaf ears, or the Gunners simply couldn't deal with the big defenders trotting up.
Gareth McAuley has been the most dangerous player in the box this season, but Craig Dawson has had his fair share of chances too.
Today, he timed his near post run perfectly and nodded in a brilliantly simple goal to give the Baggies the lead.
But before they could settle, Arsenal were level. It was Dawson, the goalscorer, who got sucked inside and Nacer Chadli, who was playing on the wing with Chris Brunt in central midfield, was caught dozing, leaving the one man you don't want to afford any space to in absolute acres of it.
Alexis Sanchez brought the ball down, checked inside, and roofed his shot. It was a clinical finish from the Chilean and his 18th Premier League goal of the season.
But that goal didn't knock the stuffing out of Albion as some would predict, far from it.
The Baggies continued to soak up pressure before flying out of the traps, sweeping up the pitch with purpose for the rest of a breathless first half.
Ten minutes after the break and Pulis took the ineffective Rondon off and replaced him Robson-Kanu.
It was a relatively early change for the Baggies boss, but it was an inspired one.
Less than a minute later, Robson-Kanu capitalised on a Mustafi mistake and brought the ball down.
He ferried it out to the brilliant McClean, who cut inside, and played it to Chadli. The Belgian lifted it over the Arsenal defence and they got themselves in a tangle, allowing Robson-Kanu to steal in and poke the ball in.
McClean was standing offside but he let the ball run through his legs and the goal stood.
Albion have struggled without the directness and pace of Matt Phillips recently, and Tony Pulis was dealt another blow in the week when James Morrison hurt his ankle. Between them those two have 10 goals and 10 assists this season.
But today, McClean provided the pace on the wing and Chadli provided the guile in midfield.
They were allowed to flood forward because behind them, Livermore was in supreme form two days after his call-up to the England squad, and he refused to give any of the Arsenal players a moment's peace.
But there were brilliant performances all over. Jonny Evans and Gareth McAuley were steadfast at the back, Dawson scored two and kept tabs on Sanchez while Nyom was typically entertaining at left-back.
Before today, owner Guochuan Lai had never seen Albion win. Since he bought a majority stake in the club for £175million last summer he's been to the home games against Everton, Tottenham, the two Manchester clubs, and now Arsenal.
He likes the big games. Unfortunately for him, Albion's record against the top seven has been dismal this season. But not anymore.
Arsenal may be in turmoil, but they still have a team brimming with quality. Albion's first win this season against a team in the top seven leaves them seven points away from their record tally in the Premier League, and what this performance does is prove that yes, they are desperate to chase it down.
12 GOAL ALBION - Craig Dawson make a late near-post run and nods in Nacer Chadli's corner.
15 GOAL ARSENAL - Alexis Sanchez is left in acres of space at the back post and he's easily picked out. The Chilean steps inside before roofing his shot.
37 Arsenal goalkeeper Petr Cech limps off with injury and is replaced by David Ospina.
54 Tony Pulis brings Hal Robson-Kanu on for Salomon Rondon
55 GOAL ALBION - The substitute toe-pokes the ball past Ospina after Chadli lifts it over the Arsenal defence. McClean is standing offside but he lets it go through his legs and the goal stands.
66 Danny Welbeck crashes a header off the crossbar from a corner.
67 Robson-Kanu nearly adds a second, but Ospina saves his shot and then Chadli rounds the keeper but his effort is cleared off the line.
75 GOAL ALBION - Dawson gets his second of the afternoon with another header from a corner, this time McClean's.
Man of the match
James McClean - Plenty of contenders but the winger was dangerous on the counter-attack and determined in defence.
Position in the table
Albion (4-1-4-1): Foster; Dawson, McAuley, Evans, Nyom; Livermore; Chadli (Field 89), Fletcher (c), Brunt (Yacob 72), McClean; Rondon (Robson-Kanu 54). Unused subs: Myhill, Olsson, M Wilson, Leko.
Arsenal (4-2-3-1): Cech (Ospina 37); Bellerin, Koscielny (c), Mustafi, Monreal; Xhaka, Oxlade-Chamberlain; Walcott (Giroud 65), Ramsey, Sanchez; Welbeck. Unused subs: Mertesacker, Gabriel, Coquelin, Elneny, Iwobi.
Referee: Neil Swarbick (Lancashire)
Attendance: 24,065 (2,766 Arsenal)Subscribe to our Newsletter