No team has ever won the title three years on the trot before - and for long periods Saints looked like turning that Leeds dream into a disaster.
But Smith made the fairytale come true as he signed off his rugby league career with two dramatic tries.
The centre, who joins rugby union side Wasps next month, scored his first touchdown late in the first half to pull them back to 8-8 after an edgy start.
But his second, with just seven minutes to go, was the one that proved the killer for Saints - the team Brian McClennan's boys have now beaten in the Grand Final three years running.
Smith looked offside but video ref Phil Bentham gave the try after an agonising wait for the Rhinos faithful. It was a fittingly edgy end to a match that had seen Saints go into an early lead, the Rhinos fight back and the lead change hands three times before Smith's second try.
With little love lost between these two sides, there was a fair chance that tempers would easily boil over into a battle.
But the opening looked more like a movie scrap as Brent 'Superman' Webb took on Sean Long, a player who wouldn't look amiss in Michael Jackson's Thriller video.
Leeds full-back Webb was desperate to live up to his super- hero nickname after injury ruled him out of last year's Final.
His enthusiasm got the better of him when he gave away a penalty in the opening seconds for a high shot on Ade Gardner.
But minutes later the Kiwi showed just how dangerous he can be, given a bit of space. Ryan Hall wasted the try-scoring chance Webb had created.
Long - a scary sight with his dreadlocks and left eye that refuses to close because of a facial injury - was just as keen to make his mark.
The controversial scrum-half was playing his last Saints game before joining Hull and almost made a dream start.
But his deft kick into Leeds' in-goal area, after a spell of Saints pressure, was inches too long for Keiron Cunningham to finish off.
Saints were looking the more threatening, although Leeds skipper Kevin Sinfield will be annoyed at the part he played in their opening try.
Jon Wilkin's chip ricocheted off Sinfield's leg, giving Kyle Eastmond just enough time to nick it off Scott Donald and race in for the score.
The young centre, who has effectively ended Long's Saints career because bosses rate him so highly, added his own conversion to put his side 6-0 up.
The champions responded immediately and only a desperate Gardner lunge stopped Scott Donald touching down a Rob Burrow kick.
Leeds forward Ryan Bailey then thought he'd broken his season- long try duck only for the effort to be ruled out for an infringement by Webb. Eastmond nudged Saints further ahead with a 26th-minute penalty but the Leeds pressure was starting to tell on the over-worked Saints defence.
The Rhinos eventually got their reward, but Saints must still be wondering how hooker Matt Diskin managed to burrow his way through three tacklers.
Sinfield hit the post with his attempt at the extra two points but suddenly the Rhinos had an extra zip in their step and looked as if they believed a third successive Grand Final victory was on the cards.
Gardner's sometimes suspect defence was targeted again and when Danny McGuire tested him with a long kick to the corner, the winger came up short.
His attempted clearance was too soft and last year's man-of- the-match, Smith, pounced for his first try.
Super League's leading goal kicker Sinfield - usually so deadly with his kicking - was again off target to send the sides in 8-8 at the break.
It showed how nervous the sides were, and how close they expected the game to be, when Sinfield opened the second half with a drop goal. With only one point scored, it was hardly a game changer, but it did give Leeds the lead for the first time.
However, it was a tactic that probably gave four-times winners Saints renewed hope and belief that the champions were vulnerable.
Gardner may be dodgy at times in defence but in attack he can be lethal and it needed a superb tackle from Hall and Webb to stop him touching down moments later.
Saints came into the game as underdogs after only winning six of their previous 12 games. But they kept on showing they had plenty of bite.
Leeds, who by contrast were on fire in the latter stages of the season, had their work cut out holding them in defence and just as much trouble breaking them down in attack.
Leon Pryce, making a record ninth Grand Final appearance, was starting to come more into it for Saints and twice he almost set up tries - only for Leeds to hold firm.
Rob Burrow's high tackle on Long gave them the chance they needed to grasp the lead, with Eastmond landing a 59th-minute penalty to put his side back in the lead.
Saints were clearly not willing to run the penalty and risk coming away with nothing and Leeds were just as wary when they got a chance.
Mind you, Sinfield would have been mad to resist going for goal with Keiron Cunningham's interference coming right in front of the sticks.
Sinfield was spot on to wrestle back the one-point lead and leave this game on a knife-edge.
It was looking like either a mistake or a moment of brilliance woud be needed to separate the teams and Eastmond looked like he'd come up with the latter.
His scampering run down the line, evading Smith and Webb, looked a certain try only for video replays to show he had narrowly gone into touch.
Leeds answered the threat with a moment to savour of their own from Smith - even though he'd looked offside when McGuire kicked ahead.
But the video ref thought otherwise and awarded the try, after also checking the ball had been properly grounded, and Sinfield added the extras.
Rob Burrow rounded off the win with a 78th-minute drop goal.
This article has 2 comments
Leeds were awesome. To defeat Saints 3 times in 3 consecutive finals rubber stamps what we all know. The Rhinos are currently untouchable. The video ref called it spot on. Marching on together!
By southstander. Posted October 11 2009 at 10:51 AM.
meli was poor for saints 2 bad errors and gifted leeds 2 tries, but the video ref had a shocker and spoiled a good game
By saint lee. Posted October 11 2009 at 10:16 AM.