The Swedish world record holder was faultless through his winning height at the Gyula Zsivótzky National Athletics Centre, then took three unsuccessful attempts at 6.32m — one centimetre above his own world record of 6.31m.
Emmanouil Karalis of Greece finished second with 6.15m. Norway’s Sondre Guttormsen took bronze on countback after also clearing 5.95m, the same height as Australia’s Kurtis Marschall and the United States’ Zach Bradford.
It was only the second competition in history — and the first outdoors — in which five athletes cleared 5.95m or higher.
Duplantis vaulted to the sound of Gold, the championship anthem he wrote and recorded. He earned $150,000 for the win as part of a $10 million prize pot across 28 events.
“It was amazing. I really like competing in Budapest,” Duplantis said. “The whole show was spectacular. It was a really fun competition tonight. It was a little bit chilly, but I had a great time.”
He also said he had approached the event with “a combination of a lot of nerves and excitement” and called the Ultimate title “a missing piece”.
Karalis cleared 6.15m at the first attempt and applied pressure, but failed at 6.20m and 6.25m. Duplantis then skipped 6.25m and went straight to the world-record height after receiving good-luck wishes from pole vault legend Sergey Bubka.
The 26-year-old now holds two Olympic titles, three outdoor world golds, four world indoor titles and the first Ultimate Championship crown.
The three-day meeting continues in Budapest through Sunday.