A second-half hat-trick by Ireland striker Robbie Keane gave Tottenham Hotspur a thrilling 4-3 win over Everton in the day's earlier Premier League clash at White Hart Lane.
Henry's electrifying pace and cool finishing gave Arsenal a sixth-minute lead. France team mate Robert Pires volleyed the second in the 28th minute to set up a comfortable win.
Cameroon defender Lauren headed Arsenal's third midway through the second half, before Henry swept home his 100th goal since joining the club from Juventus in August 1999.
The resounding win restored Arsenal's five-point lead over Manchester United at the top of the table, with third-placed Chelsea another three points further back on 41.
Henry's achievement, a week after Dutchman Dennis Bergkamp claimed his 100th goal for Arsenal in their 2-0 FA Cup win over Oxford United, was hailed by manager Arsene Wenger.
"It's fantastic what he has achieved," Wenger told Sky Sports. "And the fact that the two together have scored their 100th goals in the last two weeks is great.
"It was a difficult game but it was down to scoring first and then not conceding a stupid goal on a set-piece or a long ball.
"We had a difficult period in the second half, when it was 2-0. But when we scored the third goal, it was over."
But Wenger believes the title race is far from over with 15 matches still to play.
"We're in a good position, but there's a long way to go. In England, the turning point is in Easter... our spirit is great, the quality is there, so we are optimistic. But we know as well we have to keep a high level of concentration as the competition is hard."
City manager Steve Bruce had only one complaint after the match, which was delayed by 30 minutes due to a floodlight failure just before the scheduled kickoff.
"After about five minutes I was looking for the electrician to pull the plug again," he quipped.
Spurs were behind after only 10 minutes of their game and twice squandered the lead before Keane's opportunist late strike gave them a deserved victory after three straight defeats.
Newly-signed American striker Brian McBride put Everton ahead on his Premier League debut, but Gus Poyet levelled and Keane fired the hosts in front just after the break.
Steve Watson then equalised for Everton before Keane drilled home a superb low shot from outside the area, only for Canadian international striker Tomasz Radzinski to level matters.
With seven minutes left, Keane pounced on a defensive error by Alan Stubbs to beat former Spurs keeper Espen Baardsen, deputising for Richard Wright who was injured in the pre-match warm-up.
"It was my first hat-trick in the Premier League so it's extra special -- and my family came along today from Dublin," Keane told Sky Sports.
The Irishman, who cost 7 million pounds ($11.26 million) when he joined from Leeds United last August, added: "It's nice, but we made it hard for ourselves. Everton worked hard and we rode our luck sometimes, but luckily enough we got the three points."
Keane's manager Glenn Hoddle was delighted with his striker's treble.
"That actually has been waiting to happen all season...he could have had five goals today," Hoddle said. "It was a wonderful individual performance."
The win was an important one for Spurs who were humiliated in last weekend's 4-0 FA Cup defeat at Southampton following League defeats by Southampton and Newcastle United.
"When you lose two or three games, everybody starts talking about team spirit," Poyet said. "But we showed you there we can fight, we can run, we can play, we can score.
The victory moved Spurs up to eighth in the standings on 35 points, trailing Liverpool only on goal difference and just a point behind sixth-placed Everton.
