He cleared 6.15m on the second attempt, having come desperately close with his first, to break Sergey Bubka's outdoor pole vault world best of 6.14m set in Sestriere in July 1994.
It caps a wonderful season for the Swede who is unbeaten since last year's World Championships in Doha where he took silver behind Sam Kendricks.
Now he has eclipsed Bubka's mark and the ease with which he did it suggests that the first 6.20m+ vault is very much within his reach.
Afterwards he said, "World record - finally! It is soo cool. I wanted to get over these 6.15m so badly.
"Everybody kept talking about it, it was a big chip on my shoulder and I feel I had to do it to have people stop asking me this question. When I did it, it was more relief than joy." - Mondo Duplantis
The sky's the limit for Mondo Duplantis
The question for athletics fans is 'How high can Mondo go?'
Duplantis won the competition as the only man clear at 5.85m, ahead of Ben Broeders who took second on countback from EJ Obiena of the Philippines with Lavillenie in fourth.
Broeders' 5.80m was a new Belgian record.
The European champion then easily cleared 6.00m at the first time of asking.
He had tried 6.15m a number of times in recent weeks, including one attempt in near-darkness in the centre of Lausanne, without coming close.
But on his first try in Rome, he was well over the bar and just brushed it off with his knee on the way down to suggest that tonight might be the night.
And it was second time lucky as he cleared it with room to spare to give him both world records in the pole vault.
At just 20 years old, Duplantis is very much the present and the future of his discipline.
He's also popular with his rivals with Obiena the first to hug him after his latest record-breaking feat followed by the rest of the field including former world record holder Lavillenie.
There was one downside to his world record with neither his mother, former heptathlete Helena Hedlund Duplantis, or father Jeff, a former pole vaulter himself, there to see it.
He said, "Usually one of them is with me. I am a bit disappointed about that. My dad has never been with me when I jumped a WR.
"It is crazy. It was a really strong competition for me, so long. In the last two jumps I found my rhythm again. Maybe I will party a bit, just hang out with the guys, but trying to stay a little focused because I have one last meeting in Doha in one week. I will stay in Rome until I fly to Doha. After this last meeting in Doha, I can really party and chill.
"It has been a long time coming. Coming into the season we did not know if we were able to do any competition at all. This world record is really unexpected and I am very grateful."