FA Cup - Henry sinks Leeds with fairytale winner
Arsenal had dominated possession against a stodgy visiting side but needed the predatory instincts of Henry - who had replaced Marouane Chamakh on 68 minutes - to seal their progress in a competition they have won 10 times as the on-loan French striker slipped the ball beyond Leeds keeper Andy Lonergan with 12 minutes left.
Henry and his team-mates will face Aston Villa in the fourth round at home on the weekend of January 28/29 courtesy of the club icon's 227th goal in an Arsenal shirt.
The scenes of celebration were something to behold after Henry bounded onto Alex Song's pass to beat Lonergan with a trademark finish with his right foot that was an item of real beauty from inside the area.
He is only on loan from New York Red Bulls until the outset of March, but the short-term deal already seems to be a masterstroke by manager Arsene Wenger, who joined in the staggering moments of joy that saw Henry mobbed by his team-mates with the home supporters celebrating like they had lifted the FA Cup.
The watching former England skipper David Beckham looked as delighted as Henry, but Leeds will feel hard done by having seemed likely to force a replay despite coming to London to defend stoutly and hit on the break.
With the Dutch forward Robin van Persie rested, Arsenal looked to Andrei Arshavin and Marouane Chamakh to cut the Championship side open, but the pair suffered a frustrating night in front of goal as they huffed and puffed with little success.
That was until Chamakh made way for the bearded Henry, who is now a sprightly 34 with a statue cut outside of the stadium to honour his first stint at the club.
Arshavin had squandered a glorious chance to find the opening goal on five minutes as he walloped a shot wide from Chamakh's pass before Sebastian Squillaci nodded past a post from Mikel Arteta's corner on 14 minutes.
The outstanding Aaron Ramsey then lifted a shot over the bar from distance with Arteta slapping a shot wide from 20 yards as the general theme of Arsenal pressure and palpable frustration among the home supporters continued.
Leeds' best moment of the first period saw Luciano Becchio slam a shot over from inside the home area after a energetic run by Mika Vayrynen, but that was a rare moment of adventure from a visiting side whose general stubbornness belied their average age of only 24.
Arsenal continued to binge on possession in the second half with Lonergan diving low to his left to claw out a shot by Arteta on 53 minutes before doing likewise to repel a vicious effort by Alex Oxlade-Chamberlain as the home team continued to tot up their unsuccessful attempts on goal.
Leeds could have saved the game after Henry's big moment with substitutes Ross McCormack and Mikael Forssell forcing Wojciech Szczesny to make his first real saves of the night in the death throes of the match before the celebrations began as Henry raised his arms to the sky in celebration amid further scenes of unfettered joy.
It was little wonder Wenger said the dressing room was full of 'euphoria' in describing the mood among the Arsenal players at full-time.