Match ends, Arsenal 2, Crystal Palace 0.
Olivier Giroud's incredible scorpion kick set Arsenal on the way to a victory over Crystal Palace which moved them up to third in the Premier League.
With a cross from Alexis Sanchez delivered behind him, Frenchman Giroud elastically reached the ball with his left foot, looping it over his head and in off the underside of the bar.
An Alex Iwobi header gave Arsenal a scrappy second before Palace briefly rallied to force saves from home goalkeeper Petr Cech.
The win moves the Gunners back to within nine points of leaders Chelsea, while Palace stay 17th, two points above the relegation zone.
The visitors have won only once in 13 league games, with manager Sam Allardyce awaiting his first victory since taking over from Alan Pardew.
Giroud's magnificent moment of magic
Giroud marked his return to the Arsenal starting line-up on Boxing Day by scoring the only goal in the win over West Bromwich Albion, and followed up here by pulling off one of the most memorable moments of this or any other season.
Indeed, it was made all the more remarkable for its echoes of a similarly breathtaking goal scored by Manchester United's Henrikh Mkhitaryan in the defeat of Sunderland on Monday.
If anything, Giroud's was even more impressive, an acrobatic finish to a head-high cross delivered from the left by Sanchez at the end of a pacy Arsenal counter-attack.
As the ball arrived, a sprinting Giroud turned to stick out his left foot, flicked the ball over his head and saw it arc over the leap of Palace goalkeeper Wayne Hennessey, off the woodwork and into the net.
"It was an unbelievable finish," said former Arsenal defender Martin Keown on BBC Radio 5 live. "It has to be up there with the goal of the season already.
"He's hooked that with a gadget foot - the ball is behind him and he has no right to get his foot to it."
'The best goal I've scored' - what they said
Olivier Giroud told BBC Sport: "It is not difficult to say it is the best one. I was a bit lucky but it was the only thing I could do, the ball was behind me and I tried to hit it with a backheel.
"Maybe Henrikh Mkhitaryan's goal inspired me, it's the only thing you can do in that position. It is nice for me and the team because we start the year with a win."
Crystal Palace goalkeeper Wayne Hennessey on Sky Sports: "It was a wonder goal - there seems to be a lot going in recently. It's a fantastic strike."
Arsenal manager Arsene Wenger: "It was a great counter-attack at great speed, his reflex surprised everybody who knows football and that's what makes the goal great.
"I have been a bit spoiled over the years by the exceptional quality of the players I've had, but it will be remembered as an exceptional goal.
"Olly is very good in front of goal, but I've never seen this kind of goal from him."
Arsenal back on track
Arsenal lost ground in the title race with defeats by Everton and Manchester City, and began this game in fifth place following Tottenham's win at Watford.
Giroud's goal was the highlight of an otherwise lacklustre first half in which the only other moment of note was the Frenchman missing his kick attempting to meet a cross inside the six-yard box.
Still, the Gunners' threat was always apparent, particularly in the shape of the forward running of full-backs Hector Bellerin and Nacho Monreal, who tormented the Palace defence throughout.
Monreal was involved in the second goal, providing a cross that was not dealt with, Iwobi heading in despite the efforts of Palace defender Joel Ward on the line.
Any encouragement for Allardyce?
Palace had the chance to win Allardyce's first match in charge, only for Christian Benteke to have a penalty saved in the 1-1 draw with Watford.
At Arsenal, a team Allardyce has never beaten away in 13 Premier League attempts, what he already knew was reinforced - his new team are a threat going forward but need to improve at the back.
The 35 goals Palace have conceded is the most by any team outside the relegation zone. Though they were often organised, an inability to deal with Arsenal's movement ensured Hennessey was kept busy and the defending for the home side's second goal was shambolic.
After that, Palace had their best spell of pressure. Wilfried Zaha and Andros Townsend provided the drive, with Townsend, Benteke and Yohan Cabaye all calling Cech into action.
There is plenty to suggest Palace can move clear of trouble if Allardyce can add his trademark tightness to their backline.
"Our season won't be defined by results against the top six," he said. "What we do when we play the teams in the bottom half of the league will be the defining reason of whether or not we get out of the bottom half.
"I have every confidence in the players that it will turn around and hopefully as quick as possible."
Man of the match - Olivier Giroud
Olivier's reward - the stats
- Olivier Giroud has scored eight goals in his past six starts for Arsenal in all competitions.
- Sam Allardyce has never won at Arsenal as a manager in all competitions, drawing four and losing 12 of his 16 visits.
- Since joining the club, Alexis Sanchez has had a hand in 88 goals for Arsenal in all competitions (56 goals, 32 assists) - 26 more than any other Gunner.
- Arsenal have won 130 of their 200 Premier League games at the Emirates under Arsene Wenger (65%) - they won 72% of their league games at Highbury under the Frenchman (134/186).
- The Gunners have kept consecutive Premier League clean sheets at home for the first time this season, last doing so in their final three games of 2015-16.
- Crystal Palace have failed to keep a clean sheet in their past 20 Premier League away games, since a 0-0 draw at Bournemouth in December 2015.
- Allardyce has failed to win either of his first two Premier League games in charge of a club for the first time in his career.
Both teams are in action on Tuesday. Arsenal make the trip to Bournemouth (19:45 GMT), while Palace host bottom club Swansea (20:00).
- 18MonrealBooked at 83mins
- 35ElnenySubstituted forCoquelinat 72'minutes
- 9PérezSubstituted forRamseyat 72'minutes
- 17IwobiSubstituted forOxlade-Chamberlainat 77'minutes
- 5TomkinsBooked at 90mins
- 10TownsendSubstituted forLeeat 71'minutes
- 7CabayeSubstituted forMutchat 65'minutes
- 17BentekeSubstituted forCampbellat 77'minutes
- Andre Marriner
- Shots on Target
Second Half ends, Arsenal 2, Crystal Palace 0.
Attempt saved. Alex Oxlade-Chamberlain (Arsenal) left footed shot from the centre of the box is saved in the bottom left corner. Assisted by Alexis Sánchez.
Attempt blocked. Granit Xhaka (Arsenal) left footed shot from outside the box is blocked. Assisted by Alexis Sánchez.
Corner, Arsenal. Conceded by James Tomkins.
James Tomkins (Crystal Palace) is shown the yellow card for a bad foul.
Aaron Ramsey (Arsenal) wins a free kick on the right wing.
Foul by James Tomkins (Crystal Palace).
Attempt missed. Aaron Ramsey (Arsenal) right footed shot from the centre of the box is close, but misses to the right. Assisted by Alex Oxlade-Chamberlain.
Nacho Monreal (Arsenal) is shown the yellow card for a bad foul.
Foul by Nacho Monreal (Arsenal).
Wilfried Zaha (Crystal Palace) wins a free kick in the attacking half.
Substitution, Crystal Palace. Fraizer Campbell replaces Christian Benteke.
Substitution, Arsenal. Alex Oxlade-Chamberlain replaces Alex Iwobi.
Attempt blocked. Alexis Sánchez (Arsenal) right footed shot from outside the box is blocked.
Héctor Bellerín (Arsenal) wins a free kick in the attacking half.
Foul by Joel Ward (Crystal Palace).
Foul by Francis Coquelin (Arsenal).
Lee Chung-yong (Crystal Palace) wins a free kick in the attacking half.
Substitution, Arsenal. Aaron Ramsey replaces Lucas Pérez.