Match ends, Arsenal 3, West Ham United 0.
Arsenal 3-0 West Ham United
Arsenal boosted their Champions League hopes with a deserved victory over West Ham, who remain in relegation trouble after a fifth consecutive Premier League defeat.
After a quiet first half, Mesut Ozil, on his 150th appearance for the Gunners, fired home from the edge of the box after being gifted possession by Jose Fonte.
And the German, after playing a one-two with Alexis Sanchez, crossed for Theo Walcott - captain for the day in the absence of the injured Laurent Koscielny - to turn home from eight yards out.
Olivier Giroud curled in a fantastic third after being picked out by fellow substitute Alex Oxlade-Chamberlain.
The Gunners are now up to fifth in the table, only four points behind fourth-placed Manchester City, with a game in hand on Pep Guardiola's side.
West Ham are five points above the bottom three, although it could have been a lot worse had Swansea not collapsed late on to lose 3-1 to Tottenham.
Arsenal rediscover form at crucial time
The Gunners had only won one and drawn another in their past six Premier League games, to leave their hopes of Champions League qualification - having reached the last 17 tournaments - in real jeopardy.
There were more protests against long-serving manager Arsene Wenger - with some Gunners fans not taking their seats until the 13th minute. It has been 13 years since they last won the league.
But it did not distract the team too much, admittedly against opposition in even worse form than themselves.
Arsenal had the best of the first half, but it was after the break they took control of the game.
Hammers keeper Darren Randolph was unhappy with Ozil's opener as he felt Sanchez was offside and blocking his view, but referee Martin Atkinson did not care for his appeals.
The two Gunners stars both linked up to set up Walcott's second, and then Giroud scored the game's outstanding goal to clinch the match. The French striker, who replaced Danny Welbeck, has scored more Premier League goals as a substitute than anyone else this season - five.
Arsenal should have had a penalty in injury time when Sam Byram brought down Nacho Monreal.
The Gunners had to play their third-choice keeper, Emiliano Martinez, after injuries to Petr Cech and David Ospina. But the 24-year-old, on his first Premier League appearance since 2014, only had to make two saves in the game.
Will West Ham ever win again?
West Ham have not won a game in more than two months and have Tottenham to thank for them not being dragged closer into the relegation zone.
Before Spurs' comeback against Swansea [West Ham's opponents on Saturday], the Hammers looked set to be only three points above the relegation zone. Instead it is five.
In the first half, the Hammers were OK, but they collapsed after the Gunners - who are short of confidence themselves - scored their opener.
The Hammers' only two shots on target - from Manuel Lanzini and Edimilson Fernandes - came after the game had already gone.
Michail Antonio, returning from a hamstring injury, only lasted 45 minutes before being replaced at half-time by Robert Snodgrass.
Striker Diafra Sakho made his first appearance since November after recovering from a back injury, although he only touched the ball eight times after his second-half introduction.
Man of the match - Mesut Ozil (Arsenal)
Wenger on Ozil: "I feel that he's back physically with focus.
"I know him quite well and I felt that he got hit hard from us going out of the Champions League and it took him some time to recover from that mentally.
"I feel for a few weeks now in training he's really focused again - and that comes out in the game.
"Of course [he deserves credit]. We live in a world of extremes... we are always praised maybe more than we deserve it and punished more than we deserve it when it doesn't go well - but that's our world."
'Our confidence goes quickly and comes back slowly' - manager reaction
Arsenal boss Arsene Wenger told BBC Sport: "West Ham defended well in the first half and we needed to find a solution in the second half. We were convincing after the break.
"Ozil and Sanchez are important players but everyone did well. You could not say any player had a bad performance.
"We come out of a difficult period and our confidence goes quickly and comes back slowly.
"We are in the final sprint in the Premier League. Consistency will be very important.
"We have a little handicap on the points front. We have less possibilities to drop points."
West Ham boss Slaven Bilic told BBC Sport: "Arsenal deserved to win. The first half was OK, not only because of the score but we were good. We defended well with numbers. And we were also good on counter-attacks.
"In the second half they raised the tempo and scored a goal, and they were the better team. They were sharper than us tonight.
"We wanted to keep a clean sheet and the draw as long as possible, or even better to score, and make their fans and players a bit more nervous. But they started to play with more freedom after scoring.
"Of course we are [in a relegation battle]. We don't have to hide it. It's not being negative, it's being realistic. I told the players to forget today - we have big games ahead of us. It's a massive game against Swansea on Saturday. We are in a fight to keep our Premier League status. We have to start winning games.
"To get that confidence back is the key point. One win will change everything for us. Because three points at this stage of the season are massive."
Match of the Day analysis
Former Arsenal striker Ian Wright: "I'm just delighted Arsenal got something from the game. Mesut Ozil does what he does. It's his demeanour which upsets people, throwing his hands up in the air. It's unfortunate for him that because of his languid style he gets a lot of stick. As a forward, I'd want him behind me.
"I do feel for Slaven Bilic. I have a lot of time for him. The board have said they will back him. I just hope it's not lip service."
Arsenal reach century of goals - the stats you need to know
- Arsenal became the first Premier League side to score 100 goals in all competitions this season (currently 101).
- Theo Walcott has scored more Premier League goals against West Ham than he has against any other side (six).
- Slaven Bilic's side have failed to keep a clean sheet in any of their past 12 away Premier League games.
- Arsenal have won both Premier League games against West Ham in a season on 10 occasions - more than they have against any other side.
- No player has made more errors leading to a goal than Darren Randolph this season (three, level with Simon Francis and John Stones).
- Mesut Ozil has scored and assisted in the same Premier League game for the second time this season, with the other game being the reverse fixture against the Hammers
- Olivier Giroud has scored more Premier League goals as a substitute than any other player this season (five)
- Emiliano Martinez has kept a clean sheet in three of the four Premier League games he's started for Arsenal.
West Ham face a match against relegation rivals Swansea on Saturday at 15:00 BST. Arsenal face another London derby - at Crystal Palace - next Monday (20:00).
- 24BellerínBooked at 18mins
- 20MustafiBooked at 62mins
- 35ElnenySubstituted forRamseyat 81'minutes
- 14WalcottSubstituted forOxlade-Chamberlainat 81'minutes
- 23WelbeckSubstituted forGiroudat 74'minutes
- 22ByramBooked at 77mins
- 20A Ayew
- 16NobleSubstituted forFernandesat 80'minutes
- 10LanziniBooked at 39mins
- 30AntonioSubstituted forSnodgrassat 45'minutes
- 9CarrollSubstituted forSakhoat 64'minutes
- Martin Atkinson
- Shots on Target
Second Half ends, Arsenal 3, West Ham United 0.
Attempt blocked. Aaron Ramsey (Arsenal) right footed shot from outside the box is blocked. Assisted by Granit Xhaka.
Attempt saved. Edimilson Fernandes (West Ham United) right footed shot from outside the box is saved in the centre of the goal. Assisted by Manuel Lanzini.
Foul by Granit Xhaka (Arsenal).
André Ayew (West Ham United) wins a free kick in the attacking half.
Foul by Granit Xhaka (Arsenal).
André Ayew (West Ham United) wins a free kick in the attacking half.
Goal! Arsenal 3, West Ham United 0. Olivier Giroud (Arsenal) left footed shot from the right side of the box to the bottom left corner. Assisted by Alex Oxlade-Chamberlain.
Substitution, Arsenal. Aaron Ramsey replaces Mohamed Elneny.
Substitution, Arsenal. Alex Oxlade-Chamberlain replaces Theo Walcott.
Substitution, West Ham United. Edimilson Fernandes replaces Mark Noble.
Attempt blocked. Olivier Giroud (Arsenal) left footed shot from a difficult angle on the left is blocked.
Attempt saved. Granit Xhaka (Arsenal) left footed shot from outside the box is saved in the centre of the goal. Assisted by Mohamed Elneny.
Sam Byram (West Ham United) is shown the yellow card.
Alexis Sánchez (Arsenal) wins a free kick in the attacking half.
Foul by Sam Byram (West Ham United).
Attempt saved. Manuel Lanzini (West Ham United) right footed shot from outside the box is saved in the bottom right corner.
Substitution, Arsenal. Olivier Giroud replaces Danny Welbeck.
Attempt missed. Héctor Bellerín (Arsenal) right footed shot from the centre of the box is close, but misses to the left. Assisted by Alexis Sánchez with a through ball.
Goal! Arsenal 2, West Ham United 0. Theo Walcott (Arsenal) right footed shot from the centre of the box to the bottom left corner. Assisted by Mesut Özil.
Offside, West Ham United. Sam Byram tries a through ball, but Diafra Sakho is caught offside.
Attempt saved. Mohamed Elneny (Arsenal) header from the centre of the box is saved in the top centre of the goal. Assisted by Mesut Özil with a cross.
Attempt missed. Danny Welbeck (Arsenal) left footed shot from a difficult angle on the left is close, but misses to the left. Assisted by Mesut Özil.
Substitution, West Ham United. Diafra Sakho replaces Andy Carroll.
Attempt missed. Manuel Lanzini (West Ham United) right footed shot from a difficult angle and long range on the left is too high from a direct free kick.
Shkodran Mustafi (Arsenal) is shown the yellow card for a bad foul.
Foul by Shkodran Mustafi (Arsenal).
Robert Snodgrass (West Ham United) wins a free kick on the left wing.
Attempt saved. Danny Welbeck (Arsenal) left footed shot from the centre of the box is saved in the centre of the goal. Assisted by Theo Walcott with a through ball.
Attempt blocked. Andy Carroll (West Ham United) left footed shot from the right side of the box is blocked. Assisted by Robert Snodgrass with a cross.
Goal! Arsenal 1, West Ham United 0. Mesut Özil (Arsenal) left footed shot from outside the box to the bottom left corner.
Attempt blocked. Mohamed Elneny (Arsenal) right footed shot from outside the box is blocked. Assisted by Granit Xhaka.
Corner, Arsenal. Conceded by Arthur Masuaku.
Offside, West Ham United. Robert Snodgrass tries a through ball, but Sam Byram is caught offside.
Attempt blocked. Alexis Sánchez (Arsenal) right footed shot from the left side of the box is blocked. Assisted by Mesut Özil.
Mesut Özil (Arsenal) wins a free kick on the left wing.
Foul by José Fonte (West Ham United).
Delay over. They are ready to continue.
Delay in match Arthur Masuaku (West Ham United) because of an injury.