Lahiri followed up his brilliant 62 in the third round with a four-under-par 68 to finish the tournament on 16 under, just clear of Wiesberger (74) who had led by five shots at one point on the last day but could not hold on.
The 27-year-old Lahiri, who just three months ago came through Qualifying School, said of his triumph: “I don’t think it’s sunk in just yet, but I’m pretty sure when it hits home it’s going to be a really happy moment for me.”
Despite his 10-under-par 62 on Saturday, Lahiri came into the fourth round still trailing leader Wiesberger by five shots but a run of four birdies in his opening five holes saw the Indian turn up the heat on his title rivals.
Lahiri was unable to keep up that pace on the back nine but a fantastic 40-foot birdie putt from off the green on the 17th put him into the lead for the first time, and, after Wiesberger left a birdie attempt short on 18 that would have brought about a play-off, Lahiri was able to celebrate.
“I think I’ve got a bad habit of making it hard for myself but happy I got over the line, as ugly as it was towards the end,” said Lahiri, who admitted it was his third round that was the key to his success.
“That was now, in hindsight, one of the most important rounds so far in my career and it’s fantastic when you play well at the right time.”
Ranked 73rd heading into this week’s event at the Kuala Lumpur Golf and Country Club, Lahiri will now move into the world’s top 40.
With the top 50 automatically qualifying for the Masters when the cut-off is made in early April, the 27-year-old has a great chance of making it to Augusta National.
“That’s definitely one of my targets,” Lahiri said.
“I don’t know how far I’ve moved up [the rankings], but I’m pretty confident now with this win I should have a good chance.”
While Lahiri lifted his first piece of European Tour silverware, the in-form Wiesberger was left to wonder what might have been.
The Austrian, who recently moved into the top 50 of the world rankings for the first time, led by two shots from Spaniard Alejandro Canizares overnight and extended his advantage to five after birdies on the opening two holes.
However, a double-bogey seven after finding water on the fifth was a costly setback and further bogeys on the par-four 12th, 14th and 17th allowed Lahiri to leapfrog him.
Wiesberger still had a chance to force a play-off with that 20-foot birdie putt on the last, but he left it short.
He said: “It hasn’t quite finished the way I intended to. After the hiccup on five, I didn’t hit it anywhere near as good as the last 15 rounds.
“It’s tough to say, but it is what it is and unfortunately I beat myself out of it today.”
England’s Paul Waring and Canizares shared third place on 13 under following respective final rounds of 73 and 74.
Former world No 1 and defending champion Lee Westwood (75) was two shots further back, tying with Gregory Bourdy (69), Richard Lee (71) and Paul Peterson (72) on 11 under.
• Australia’s Richard Green and his Norwegian fiancée Marianne Skarpnord made golf history yesterday by winning the men’s and women’s titles at the Victoria Open on the same course on the same day. The tournament is a professional rarity in which the men’s and women’s tournaments are contested concurrently.
Skarpnord first won the women’s title by two strokes from rising Australian star Su Oh, then waited nervously on the 18th green while Green took the men’s title on the second hole of a sudden-death play-off with compatriot Nick Cullen. Green said: “I really think it’s fascinating that we’ve both done it. Especially with Marianne winning, experiencing her thoughts and feelings on the week at night and talking to each other about it has been very different.”