Everton moved back into the top four with a 2-1 win over Southampton and Tottenham Hotspur beat Stoke City 3-0 to get their first victory since appointing Tim Sherwood as the English game served up more drama in its congested festive schedule.
Chelsea F.C. fell behind to a goal from Martin Skrtel after four minutes, but rallied with first-half strikes from Eden Hazard and Samuel Eto'o to inflict a second defeat in four days on Liverpool F.C. following their loss at Manchester City.
Arsenal's win came courtesy of France striker Giroud, who had not scored in all competitions since Nov. 23, but got the faintest of touches to glance a Theo Walcott free kick into the net midway through the second half.
They now top the table with 42 points from 19 games, one clear of Manchester City with Chelsea a point further adrift in third.
Liverpool, top on Christmas Day, dropped to fifth, a point behind local rivals Everton who moved fourth with 37 points thanks to a second-half winner from Romelu Lukaku.
A Roberto Soldado penalty and goals from Mousa Dembele and Aaron Lennon lifted Tottenham to seventh on 34 points.
Liverpool have had the wind taken out of the sails with back-to-back away defeats against fellow title challengers with both games starting brightly for them before turning sour.
They had their tails up after four minutes when Skrtel put them ahead, tapping home from close range after Luis Suarez beat Branislav Ivanovic to a Philippe Coutinho free kick.
That sparked Chelsea into life and they rapidly got on top, with Brazilian David Luiz, drafted into midfield to replace the suspended Ramires, showing why Chelsea boss Jose Mourinho might be tempted to use him there more often.
Chelsea attacked in waves and drew level through Hazard on 17 minutes with the Belgium international curling home after the ball broke fortuitously to him on the edge of the area.
They deservedly took the lead 11 minutes before the break when Eto'o darted in front of his marker Skrtel to poke an Oscar cross past Liverpool keeper Simon Mignolet into the net.
Chances were limited in the second half, Liverpool's best effort coming from Mamadou Sakho who hit the woodwork with a looping header seconds before Eto'o forced an excellent save from Mignolet with a powerful near-post shot.
Liverpool were incensed not to be awarded a penalty late in the match when Eto'o appeared to foul Suarez right in front of referee Howard Webb, but the official waved away their protests and Chelsea closed out the win.
"We were lucky to win the game because it is very tight," Chelsea manager Jose Mourinho told Sky Sports before praising the players for putting on a fantastic show for fans.
"The players are like monsters - they fight until the last seconds."
Arsenal's visit to Newcastle promised goals after the North Londoners won 7-3 when the teams clashed on the same day last year, but this game soon descended into a more stolid affair with both defences well on top.
Arsenal kept possession neatly, but without injured playmaker Mesut Ozil lacked incision and failed to create a chance of note in the first half.
It looked to be heading towards a draw when Arsenal struck the decisive blow. Walcott's free kick was perfectly angled into the box and Giroud got in between the Newcastle centre backs to feather a delicate header into the net.
There was a frenetic finale but Arsenal's defence held out to ensure they go into the New Year on top of the table for the first time since 2007-08, to provide manager Arsene Wenger with some festive cheer.
"There was a big satisfaction because we surprised many people and we want to go on from here," he said.
"We played two away games and got six points against West Ham and Newcastle and as you can see the team is ready for a fight. Let's keep fighting and trying to develop the team."
Everton, who played more than 60 minutes of their defeat to Sunderland on Thursday with 10 men, seemed to be rejuvenated with their full quota on the field and took the lead after nine minutes.
Seamus Coleman cut inside, switched the ball to his right foot and fired an angled shot into the net for his fourth goal in his last seven Premier League games.
Gaston Ramirez levelled with a thundering shot from distance, but parity lasted only a few minutes as Lukaku ran on to a pass from James McCarthy and the Belgium striker took one touch and fired home from 12 metres.
There was a familiar feel to Tottenham's opening goal with Soldado firing home the fourth of his five Premier League goals from the penalty spot after Ryan Shawcross was penalised for handball.
Dembele worked some room on the edge of the area and fired low into the bottom corner to double the lead and Lennon angled a shot into the top corner.