Pablo Fornals put the hosts ahead midway through the first-half, and after Ayoze Perez saw red just before the break, Leicester's misery was compounded following half-time.
Story of the match:
The fast tempo was evident from the start as Michail Antonio made a surging run into the opposition half shortly after, his final ball unable to feed through teammate Said Benrahma as the forward closed in on goal.
It was the Algerian who had the first shot on target of the fixture with 5 minutes on the clock, however the Hammers' winger's effort was comfortably saved by Kasper Schmeichel.
West Ham did the double over the Foxes last season, executing a counter-attacking game plan to near perfection on both occasions, and David Moyes' team looked keen to do the same tonight. The visitors kept the ball well in their own half, but the men in Claret and Blue more dangerous on the break.
The hosts had another couple of chances around the 15-minute mark, 'skipper Declan Rice firing over and Antonio shooting wide as they began to press for an opener.
West Ham's promising start was rewarded after 25 minutes when they took a deserved lead through Pablo Fornals. The talented Spaniard showed great awareness, receiving the ball in the final third and spreading it wide to Benrahma, before finishing an expertly-delivered cross into the far corner with great guise.
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Fornals' goal to make it 1-0 ignited an already rocking 60,000 capacity crowd, and they were almost treated to a second when Tomas Soucek headed close soon after.
Leicester had a great opportunity to equalise with 30 minutes gone, Ayoze Perez slipping through Ricardo Pereira on the right, although the Portuguese defender slipped at the crucial moment and skewed his effort wide from close range.
Perez was involved again as the visitors began to threaten, the former Newcastle man dragging his effort well wide of the goal from the edge of the area. However, the Leicester forward's evening came to an abrupt end shortly before the break when he was sent off for a challenge on Fornals.
Although unbalanced, Perez caught his compatriot with a late and dangerous lunge as he attempted to retrieve possession inside his own half, and he was given his marching orders by Michael Oliver after a VAR check.
Following the dismissal, the home team enjoyed more of the ball as Leicester retreated into their own half, a man and a goal down going into the break.
Brendan Rodgers made no changes at half-time but would have had some stern words for his team as they looked to improve from a lacklustre first 45.
It was the home side who had the first attempt of the second half as Soucek poked over the bar, the Czech international linking up well with Bowen after being given greater license to attack, due to the man advantage.
Schmeichel impressed for Denmark at the summer's European Championships, and the 'keeper continued his fine form, making a fantastic save to deny Antonio's header after he met Fornals' whipped delivery inside the box.
West Ham continued on the front foot, and they doubled their lead on 56 minutes after capitalising on a disastrous Soyuncu mistake.
The Turkish defender made a huge error as he attempted to pass back to his 'keeper, but it was anticipated by Antonio who squared to Benrahma, allowing his teammate to pass into the net and make it 2-0 with ease.
The Foxes struggled to play out all evening, and were made to pay by the impressive Hammers in front of a sell-out home crowd.
Antonio nearly got his goal just after the hour-mark, robbing Tielemans in the middle of the park to start the move, and almost finishing it with a driven effort from outside the area that forced another great save from the Danish shotstopper.
Leicester made the first change of the game when Patson Daka replaced Barnes on 63 minutes, a bold attempt from the away team to find a way back into the game as they introduced another striker.
Despite dominating, West Ham allowed the away team a route back in when Youri Tielemans fired past Fabianski at the back post to make it 2-1, the Foxes refusing to accept defeat and causing doubt amongst the supporters inside the London Stadium.
The goal was Leicester's first attempt on target of the match, and gave them some confidence to find an equaliser. West Ham continued to push on, aiming to finish the game off with a third goal while Leicester battled on despite the barrage of corners.
Their resistance was eventually broken down, and the Hammers wrapped up the game with 10 minutes to go.
Declan Rice did well down the left, drilling a low cross into Michail Antonio who did the rest. West Ham's number nine held off his man, took a touch to his right, and fired a rocket into the far corner to make it 3-1.
In doing so he made himself West Ham's leading Premier League goalscorer. A historic achievement.
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The goals kept coming as the game drew to a close, the Michail Antonio masterclass continuing as he completed his brace and made it 4-1. Coufal crossed from the right, Antonio took a touch to beat his man, and slotted past the onrushing goalkeeper much to the delight of the home support.
Leicester were frustrated in the final minutes as the crowd olay'd every pass, the visitors unable to get close to their counterparts as they struggled on with 10-men.
The final whistle ended the Foxes' misery, and a loud cheer erupted from the Claret and Blue faithful as they celebrated an iconic victory for their team.
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